feat(tabs): give the vertical rail the home screen's per-session detail

The vertical tab rail (tabOrientation 'vertical') listed names and nothing
else, while the rich sidebar and both home screens already answered the
question a docked column exists to answer: which of these sessions wants me
next, and how long has it been like that. The rail is a docked column too, so
it now draws the same row.

- New per-device setting tabRailDetail ('rich' | 'simple', default rich),
  App Settings -> Appearance -> Tabs, in SettingsUpdateSchema + displayKeys and
  stamped as data-tab-rail-detail by the pre-paint script, so a detailed rail
  does not flash through simple rows on every load.
- ONE gate for both vertical surfaces: isRichTabRows() =
  isSessionSidebarRich() || isTabRailRich(). The row model, the markup and the
  20s in-place clock are the existing rich-sidebar ones, classified by
  _mobileOverviewState/_mobileOverviewSince, so the rail, the sidebar, the
  desktop home rail and the phone overview cannot disagree about what
  "working" means or which stamp measures it.
- Detail rides on its OWN attribute, exactly as the sidebar's does, so every
  existing [data-tab-orientation='vertical'] rule keeps matching both variants
  untouched. A flip of detail ALONE still forces a full render (the stamps line
  is emitted by the row template, not toggled by CSS) and re-runs
  applyTabWrapSettings(), which owns the folder line and is now rail-aware.
- CSS: every rich paint rule gains a rail twin as a COMMA-GROUPED selector,
  never :is() - an :is() list takes its most specific argument, which would
  lift the sidebar arm from (0,3,1) to the rail's (0,5,1) and let these rules
  outrank things they never used to.
- Width is why there are thresholds. At 256px the stamps line ellipsizes
  mid-word, the same reason the rich sidebar is 300px, so a rail that has never
  been sized defaults to 320 (RICH_DEFAULT_WIDTH, the existing Wide preset,
  which also keeps the settings select on a named choice). A width the user has
  chosen is never overridden: below 288px the created stamp is dropped rather
  than truncated (tab-rail-tight, CSS only) and below 240px the rows go back to
  simple (tab-rail-compact, which re-renders).
- The rich clock is armed and disarmed by applyTabOrientation() as well as
  applySessionListLayout(); a leaked interval would rewrite stamps in a list
  that no longer has any.

Also fixes a data-loss bug in the inline tab rename that predates the rail and
reproduces in every layout, header strip included: Escape set the input to ''
and blurred it, and the blur handler commits - so cancelling a rename PUT an
empty name, and the tab fell back to its folder label (measured against a live
server: ["rail-alpha","","rail-gamma"]). Escape now calls cancelRename(), which
invalidates the edit so the blur that follows the input's removal is a no-op.

Tests: rail-detail gate, the three ways it turns back off (simple, compact,
horizontal), sidebar-wins, render-on-detail-flip and the plumbing/CSS guards in
test/session-list-layout.test.ts; the rename cancel in test/inline-rename.test.ts
(browser suite), pinned by running it against the old code first. Verified live
against a real server on an isolated instance: detailed/simple/compact/header/
sidebar variants, click-select, the ... menu, inline rename, Alt+N, the in-place
stamp tick and a full settings-picker round-trip including reload.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/inline-rename.test.ts

@@ -125,6 +125,45 @@ describe('Inline rename input', () => {
     expect(renameStillActive).toBe(true);
   });
 
+  it('Escape cancels the rename instead of committing an empty name', async () => {
+    await resetState();
+    expect(await startRename('esc-cancel', 'rail-beta')).toBe(true);
+
+    // Escape used to clear the field and blur, and the blur handler commits —
+    // so cancelling a rename PUT an empty name, and the tab fell back to its
+    // folder label (measured against a live server, in the header strip as well
+    // as both vertical layouts). The observable here is the REQUEST: this
+    // harness's server has no such session, so a failed PUT would leave the
+    // local map looking innocent.
+    const result = await page.evaluate(async () => {
+      const app = (window as unknown as { app: { _activeRename: unknown } }).app;
+      const calls: string[] = [];
+      const origFetch = window.fetch;
+      window.fetch = (async (input: RequestInfo | URL) => {
+        calls.push(String(input));
+        return new Response('{"success":true}', { status: 200 });
+      }) as typeof window.fetch;
+
+      const inputEl = document.querySelector('input.tab-rename-input') as HTMLInputElement;
+      inputEl.value = 'typed-but-abandoned';
+      inputEl.dispatchEvent(new KeyboardEvent('keydown', { key: 'Escape', bubbles: true }));
+      // The blur that follows the input's removal must not resurrect the commit.
+      inputEl.dispatchEvent(new Event('blur'));
+      await new Promise((r) => setTimeout(r, 50));
+
+      window.fetch = origFetch;
+      return {
+        renamePuts: calls.filter((url) => url.includes('/api/sessions/esc-cancel/name')),
+        renameActive: !!app._activeRename,
+        inputStillInDom: document.body.contains(inputEl),
+      };
+    });
+
+    expect(result.renamePuts).toEqual([]);
+    expect(result.renameActive).toBe(false);
+    expect(result.inputStillInDom).toBe(false);
+  });
+
   it('CJK guard: regular Enter (no IME) DOES commit', async () => {
     await resetState();
     expect(await startRename('regular-enter', 'OldName')).toBe(true);