Focused text fields show their outline on every edge (#202)

The focus outline of a text field was only visible at its corners.
The mask that clips the text covered the whole field, border included,
so the 1 px stroke was cut away along every straight edge. Only the
rounded corners bent inwards far enough to survive. With the larger
radius the new theme tried, this became obvious.

- TextField puts text, selection and caret into their own container.
  Only that container is masked. Background and outline are not.
- NumberField and the rename field in lists inherit the fix.
- The theme radius goes back to 2 px.
- New debug hook __gm.focusedRect() returns where the focused widget
  sits, so a check can read its border.

Tests:
- ./check.sh: 141 files, 2080 tests, exit 0
- GM_STEPS=2: ALL PASSED, 24 checks (one new)
- The new check in 2c reads the middle of all four edges of the
  focused name field. All four must be the focus blue.
- Counter-check with the old full-field mask: the check fails, all
  four edges read #24272e.
- Editor check total is now 1286 (1285 + 1), computed, not measured.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/editor/debugHook.ts

@@ -210,6 +210,11 @@ export function installDebugHook(app: Application, state: EditorState, editor: E
     inspectorField: fieldOf,
     /** The inspector panel on screen – what tells whether a row of it can be clicked at all. */
     inspectorRect: () => rectOf(inspector),
+    /** Where the focused widget sits on screen, or `null` – for checks on its focus border. */
+    focusedRect: () => {
+      const widget = ui().focus.focused;
+      return widget ? rectOf(widget) : null;
+    },
     inspectorInfo: () => inspector.debugInfo(),
     textColor,
     overlayTexts,