fix(tabs): lower-case search text without the browser locale (#580)

CodemanTabSearch lower-cased the query and each row with
toLocaleLowerCase(), i.e. the browser's locale. Under a Turkish or Azeri
locale "API Review" lowers to "apı review", so a search for "api" missed
it, and the sidebar filter box, which used locale-independent
toLowerCase() before #580, changed matching with it. Both now use
toLowerCase(), like every other frontend search.

Test: a vm context of its own whose toLocaleLowerCase behaves like the
Turkish locale (the prototype is that context's alone) checks that "API"
still normalizes to "api" and that "API Review" matches. The test file's
overview also lists the pins the #580 fixes added.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/tab-rail-search.test.ts

@@ -16,7 +16,15 @@
  * - Only the grouped rail is a tree: hidden rows and the headers of hidden
  *   groups leave the roving walk and the posinset/setsize count.
  * - The rail matches the NAME (a web tab's title); the sidebar keeps matching
- *   name + working directory.
+ *   name + working directory. Lower-casing never follows the browser locale
+ *   (a Turkish locale lowers "API" to "apı").
+ * - A session row with a tab alert is never hidden, and keeps its group or
+ *   case box on screen (the owner's call on #580).
+ * - Escape in a box that holds text clears the search and closes nothing else:
+ *   the global key handler runs first (capture phase) and must route it.
+ * - A change in what shows redraws the connector lines, which are anchored to
+ *   row positions; an unchanged re-apply does not.
+ * - The sidebar hides a case box its filter emptied, like the rail.
  * - The input is labelled, sits at the top of #tabRail, and every new string
  *   reads in zh-CN.
  *
@@ -126,6 +134,24 @@ describe('CodemanTabSearch (pure)', () => {
     expect(result.counts.get('g')).toBe(0);
     expect(search.filter(null as never, 'x').matchCount).toBe(0);
   });
+
+  it('lower-cases without the browser locale, so a Turkish locale still finds "API"', () => {
+    // A context of its own, whose locale-aware lower-casing behaves like the
+    // Turkish locale (I -> dotless i). The prototypes are this context's alone.
+    const context = vm.createContext({ window: {}, globalThis: {} });
+    vm.runInContext(
+      "String.prototype.toLocaleLowerCase = function () { return String(this).replace(/I/g, '\\u0131').toLowerCase(); };",
+      context
+    );
+    vm.runInContext(read('constants.js'), context, { filename: 'constants.js' });
+    const turkish = (context.window as { CodemanTabSearch: TabSearch }).CodemanTabSearch;
+    expect(vm.runInContext("'API'.toLocaleLowerCase()", context)).toBe('apı');
+
+    expect(turkish.needle('API')).toBe('api');
+    const result = turkish.filter([{ key: 'r', text: 'API Review', section: null }], 'api');
+    expect(result.hidden.size).toBe(0);
+    expect(result.matchCount).toBe(1);
+  });
 });
 
 // ─── The rail, driven through the shipping CodemanApp ────────────────────────