feat(foreground): track topmost process + browser page title

Adds cross-platform foreground-window tracking and exposes it over REST
(/api/foreground) and the existing WebSocket feed.

- foreground_service.py: Windows probe via ctypes (HANDLE-correct argtypes
  to avoid 64-bit handle truncation); macOS via AppKit; Linux via Xlib
  (Wayland returns unavailable). TTL cache + per-platform fallback.
- browser_url_service.py: when foreground is a recognised browser, extract
  the page title from the window title (browser-name suffix stripped) and
  surface `is_browser` + `browser_page_title`. Optional UIA-based URL
  extraction behind MEDIA_SERVER_BROWSER_UIA env flag (off by default —
  Chromium browsers keep their accessibility tree dormant otherwise).
- websocket_manager: poll foreground every 1s inside the existing status
  loop, broadcast `foreground` on connect and `foreground_update` on
  change. Diff only on user-visible fields to avoid geometry spam.
- WebUI: new editorial card rendered under the monitor list on the
  Display tab — process name, window title, fullscreen/minimized/monitor
  chips, browser block when applicable, exe path, PID, started-ago,
  geometry, platform. 16px inter-section gap matches Settings cadence.
- i18n: 25 new keys added to both en.json and ru.json.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

media_server/services/browser_url_service.py

@@ -0,0 +1,296 @@
+"""Extract page-level metadata from a focused desktop web browser.
+
+The browser's window title is the reliable signal — every major browser
+formats it as ``"<page title> - <Browser Name>"``, so stripping the suffix
+gives us the page title for free.
+
+URL extraction was attempted via UI Automation (UIA), but Chromium-based
+browsers (Chrome/Edge/Brave/Vivaldi) keep their accessibility tree dormant
+unless a screen reader is active or ``--force-renderer-accessibility`` is
+set — neither is something we want to require from end users. The UIA
+machinery is still here behind a feature flag in case a future caller
+opts into the accessibility-flag path; by default we just return the
+page title and leave ``url=None``.
+
+Other platforms (macOS via AppleScript, Linux via AT-SPI) are out of scope
+for this iteration.
+"""
+
+from __future__ import annotations
+
+import logging
+import os
+import platform
+import threading
+from dataclasses import dataclass
+
+logger = logging.getLogger(__name__)
+
+# UIA URL extraction is opt-in because Chromium browsers keep their
+# accessibility tree dormant unless the user starts the browser with
+# ``--force-renderer-accessibility`` (or a screen reader is running).
+# Without that, `FindAll` throws and we'd burn 5s per probe retrying.
+# Set MEDIA_SERVER_BROWSER_UIA=1 to enable; default off.
+_UIA_ENABLED = os.environ.get("MEDIA_SERVER_BROWSER_UIA", "").lower() in (
+    "1", "true", "yes", "on"
+)
+
+
+# Known browser executables (lowercase, .exe-stripped). Used to decide
+# whether to spend the UIA query budget on this foreground process.
+BROWSER_PROCESS_HINTS: frozenset[str] = frozenset({
+    "chrome",
+    "msedge",
+    "firefox",
+    "brave",
+    "opera",
+    "vivaldi",
+    "yandex",
+    "browser",  # Yandex Browser sometimes reports as browser.exe
+    "arc",
+    "thorium",
+})
+
+
+@dataclass(frozen=True)
+class BrowserPageInfo:
+    url: str | None = None
+    page_title: str | None = None
+
+
+_EMPTY = BrowserPageInfo()
+
+
+def is_browser_process(process_name: str | None) -> bool:
+    """Return True when ``process_name`` looks like a supported browser."""
+    if not process_name:
+        return False
+    base = process_name.lower()
+    if base.endswith(".exe"):
+        base = base[:-4]
+    return base in BROWSER_PROCESS_HINTS
+
+
+def _strip_browser_suffix(title: str | None, process_name: str | None) -> str | None:
+    """Pull the page title out of the browser's window title.
+
+    Most browsers format their window title as ``"<page> - <Browser Name>"``.
+    We strip the trailing suffix so consumers get the page title alone. If
+    the suffix can't be matched, return the raw title unchanged.
+    """
+    if not title:
+        return None
+    suffixes = (
+        " - Google Chrome",
+        " — Google Chrome",
+        " - Microsoft Edge",
+        " - Microsoft Edge",
+        " — Mozilla Firefox",
+        " - Mozilla Firefox",
+        " - Brave",
+        " - Opera",
+        " - Vivaldi",
+        " - Yandex",
+    )
+    for s in suffixes:
+        if title.endswith(s):
+            return title[: -len(s)].strip() or None
+    return title
+
+
+# ─── UIA lookup (Windows) ───────────────────────────────────────────
+
+# UIA control type / property constants we need. Avoiding the full
+# UIAutomationClient typelib generation — those constants are stable.
+_UIA_EditControlTypeId = 50004
+_UIA_ControlTypePropertyId = 30003
+_UIA_ValueValuePropertyId = 30045
+_UIA_NamePropertyId = 30005
+_UIA_ValuePatternId = 10002
+_TreeScope_Descendants = 4
+_PropertyConditionFlags_IgnoreCase = 1
+
+
+# Lazy import + per-thread COM init.
+_uia_lock = threading.Lock()
+_uia_singleton = None
+_uia_load_error: str | None = None
+_uia_thread_local = threading.local()
+
+
+def _ensure_com() -> None:
+    """Initialise COM on the current thread (idempotent per thread)."""
+    if getattr(_uia_thread_local, "initialised", False):
+        return
+    try:
+        import comtypes  # type: ignore
+
+        # COINIT_APARTMENTTHREADED is required by UIA; comtypes' default
+        # CoInitializeEx already passes that flag.
+        comtypes.CoInitialize()
+        _uia_thread_local.initialised = True
+    except Exception as e:
+        logger.debug("CoInitialize failed: %s", e)
+
+
+def _get_uia():
+    """Return the IUIAutomation singleton, or None if unavailable."""
+    global _uia_singleton, _uia_load_error
+    if _uia_singleton is not None:
+        return _uia_singleton
+    if _uia_load_error is not None:
+        return None
+    with _uia_lock:
+        if _uia_singleton is not None:
+            return _uia_singleton
+        try:
+            import comtypes.client  # type: ignore
+
+            # CLSID for CUIAutomation. Using GetActiveObject would fail,
+            # so we cocreate. comtypes.client.CreateObject keeps the COM
+            # plumbing tidy.
+            _uia_singleton = comtypes.client.CreateObject(
+                "{ff48dba4-60ef-4201-aa87-54103eef594e}",
+                interface=comtypes.client.GetModule(
+                    "UIAutomationCore.dll"
+                ).IUIAutomation,
+            )
+            return _uia_singleton
+        except Exception as e:
+            _uia_load_error = str(e)
+            logger.info("UIA unavailable; browser URL extraction disabled: %s", e)
+            return None
+
+
+def _find_address_bar_value(hwnd: int) -> str | None:
+    """Walk the UIA tree under ``hwnd`` looking for the URL Edit control.
+
+    Strategy: find every descendant Edit control, then pick the first one
+    whose Name contains an address-bar hint, or — failing that — the first
+    one whose value parses as a URL-ish string. Browsers expose extra Edit
+    controls (search bars, find-in-page) so name matching is the reliable
+    signal; the URL-ish fallback covers locale variants we haven't seen.
+    """
+    _ensure_com()
+    uia = _get_uia()
+    if uia is None:
+        return None
+
+    try:
+        element = uia.ElementFromHandle(hwnd)
+        if not element:
+            return None
+
+        # Build a condition matching ControlType=Edit, then enumerate.
+        edit_condition = uia.CreatePropertyCondition(
+            _UIA_ControlTypePropertyId, _UIA_EditControlTypeId
+        )
+        edits = element.FindAll(_TreeScope_Descendants, edit_condition)
+        count = edits.Length if edits else 0
+        if count == 0:
+            return None
+
+        # Hints (lowercase) used to identify the address bar by its Name
+        # property. Covers en-US plus a few common locales / browsers.
+        name_hints = (
+            "address",          # Chrome/Edge: "Address and search bar"
+            "адрес",            # Chrome ru: "Адресная строка и строка поиска"
+            "адресная",
+            "search with",      # Firefox: "Search with Google or enter address"
+            "поиск или ввод",   # Firefox ru
+            "url",
+            "location",
+        )
+
+        # First pass: name-based match (high confidence).
+        candidates: list[tuple[int, str]] = []
+        for i in range(count):
+            edit = edits.GetElement(i)
+            try:
+                name = (edit.CurrentName or "").lower()
+            except Exception:
+                name = ""
+            try:
+                value = edit.GetCurrentPropertyValue(_UIA_ValueValuePropertyId)
+            except Exception:
+                value = None
+            if value is None:
+                continue
+            value_str = str(value)
+            for h in name_hints:
+                if h in name:
+                    return value_str
+            candidates.append((i, value_str))
+
+        # Second pass: URL-ish fallback. Pick the first candidate that
+        # looks like a URL; this catches browser/locale combos we haven't
+        # listed above.
+        for _i, v in candidates:
+            lv = v.lower()
+            if (
+                lv.startswith("http://")
+                or lv.startswith("https://")
+                or lv.startswith("about:")
+                or lv.startswith("chrome://")
+                or lv.startswith("edge://")
+                or lv.startswith("brave://")
+                or lv.startswith("file://")
+                or lv.startswith("ftp://")
+            ):
+                return v
+
+        return None
+    except Exception as e:
+        logger.debug("UIA address-bar lookup failed: %s", e)
+        return None
+
+
+# ─── Per-(hwnd, title) cache ────────────────────────────────────────
+
+_cache_lock = threading.Lock()
+_cache_key: tuple[int | None, str | None] = (None, None)
+_cache_value: BrowserPageInfo = _EMPTY
+
+
+def get_browser_page(
+    *,
+    hwnd: int | None,
+    process_name: str | None,
+    window_title: str | None,
+) -> BrowserPageInfo:
+    """Return the URL + page title for the foreground browser tab, if any.
+
+    Callers pass the already-resolved foreground HWND/title/process_name so
+    this service doesn't re-walk Win32 to find them. Returns ``_EMPTY`` for
+    non-browser processes or when UIA can't resolve the URL.
+    """
+    if not is_browser_process(process_name):
+        return _EMPTY
+    if platform.system() != "Windows":
+        # macOS/Linux paths not implemented in this iteration.
+        return _EMPTY
+    if not hwnd:
+        return _EMPTY
+
+    global _cache_key, _cache_value
+    key = (hwnd, window_title)
+    with _cache_lock:
+        if key == _cache_key and _cache_value is not _EMPTY:
+            return _cache_value
+
+    url = _find_address_bar_value(hwnd) if _UIA_ENABLED else None
+    page_title = _strip_browser_suffix(window_title, process_name)
+    info = BrowserPageInfo(url=url, page_title=page_title)
+
+    with _cache_lock:
+        _cache_key = key
+        _cache_value = info
+    return info
+
+
+def reset_cache() -> None:
+    """Reset the cache. Useful in tests."""
+    global _cache_key, _cache_value
+    with _cache_lock:
+        _cache_key = (None, None)
+        _cache_value = _EMPTY