Add dirty check to all remaining editor modals

Subclass Modal with snapshotValues() for: value source editor, audio
source editor, add device, profile editor, capture template, stream
editor, and PP template modals. Close/cancel now triggers discard
confirmation when form has unsaved changes. Document the convention
in CLAUDE.md.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -120,6 +120,35 @@ Add hint text to both `en.json` and `ru.json` locale files using a `.hint` suffi
 
 Do **not** add placeholder options like `-- Select something --`. Populate the `<select>` with real options only and let the first one be selected by default.
 
+### Modal dirty check (discard unsaved changes)
+
+Every editor modal **must** have a dirty check so closing with unsaved changes shows a "Discard unsaved changes?" confirmation. Use the `Modal` base class pattern from `js/core/modal.js`:
+
+1. **Subclass Modal** with `snapshotValues()` returning an object of all tracked field values:
+
+   ```javascript
+   class MyEditorModal extends Modal {
+       constructor() { super('my-modal-id'); }
+       snapshotValues() {
+           return {
+               name: document.getElementById('my-name').value,
+               // ... all form fields
+           };
+       }
+       onForceClose() {
+           // Optional: cleanup (reset flags, clear state, etc.)
+       }
+   }
+   const myModal = new MyEditorModal();
+   ```
+
+2. **Call `modal.snapshot()`** after the form is fully populated (after `modal.open()`).
+3. **Close/cancel button** calls `await modal.close()` — triggers dirty check + confirmation.
+4. **Save function** calls `modal.forceClose()` after successful save — skips dirty check.
+5. For complex/dynamic state (filter lists, schedule rows, conditions), serialize to JSON string in `snapshotValues()`.
+
+The base class handles: `isDirty()` comparison, confirmation dialog, backdrop click, ESC key, focus trapping, and body scroll lock.
+
 ## General Guidelines
 
 - Always test changes before marking as complete