Polish Pattern Template UI: dialog sizing, KC editor layout, and conventions

- Fix dialog/canvas sizing: fit-content dialog follows canvas width, canvas
  max-width: 100% prevents overflow, horizontal resize supported
- Move pattern template dropdown above FPS/mode/smoothing in KC editor
- Remove emoji from pattern template dropdown options and auto-generated names
- Remove placeholder option from pattern template select, default to first
- Rename default pattern template from "Default" to "Full Screen"
- Add UI conventions to CLAUDE.md (hint pattern, select dropdown rules)

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

CLAUDE.md

@@ -89,6 +89,29 @@ This is a monorepo containing:
 For detailed server-specific instructions (restart policy, testing, etc.), see:
 - `server/CLAUDE.md`
 
+## UI Conventions for Dialogs
+
+### Hints
+
+Every form field in a modal should have a hint. Use the `.label-row` wrapper with a `?` toggle button:
+
+```html
+<div class="form-group">
+    <div class="label-row">
+        <label for="my-field" data-i18n="my.label">Label:</label>
+        <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?">?</button>
+    </div>
+    <small class="input-hint" style="display:none" data-i18n="my.label.hint">Hint text</small>
+    <input type="text" id="my-field">
+</div>
+```
+
+Add hint text to both `en.json` and `ru.json` locale files using a `.hint` suffix on the label key.
+
+### Select dropdowns
+
+Do **not** add placeholder options like `-- Select something --`. Populate the `<select>` with real options only and let the first one be selected by default.
+
 ## General Guidelines
 
 - Always test changes before marking as complete