fix(mobile): address review blockers on the touch-device change set

Review follow-ups on PR #111 (rebased onto master post-#112/#113):

Resize arbitration redesigned (review blocker 2): the previous
'cols < _ptyCols' guard froze a mobile-only session's PTY at the spawn
default — narrow phones rendered clipped and could never re-fit. The
guard now uses connection-scoped desktop sizing claims instead:
ws-routes registers a claim on a desktop-typed resize and releases it
on socket close (or when the same connection later reports a small
viewport), and Session.resize() ignores mobile/tablet resizes only
while at least one desktop connection holds a claim. A phone alone
fully controls its size (shrink, rows-only shrink, re-grow); a phone
glancing at a desktop-driven session can no longer reflow it.
mobile-handlers' keyboard open/close resize now declares its viewport
type so it participates in arbitration. Tests rewritten to cover
mobile-only shrink/rows-only/re-grow, claim/release lifecycle, multi-
claim behavior, and untyped legacy resizes; ws-routes test covers the
claim lifecycle over a real socket.

Solo/detached header restored (review blocker 3): index.html had
removed #soloSessionTitle and #soloRedockBtn, which _applySoloMode
still references — every detached window hit a null deref. Both are
back alongside the new mobile utility toggle.

Desktop leak fixed (review should-fix): .mobile-header-utility-toggle
had no rule outside the <=768px media queries, so the raw button
rendered on desktop. styles.css now hides it by default; the mobile/
tablet queries re-enable it.

Visual-regression baselines reverted to master (review should-fix):
the 18 contributor-machine PNGs are environment-specific (8 of the
behavioral tests already report environment-sensitive failures across
machines); re-baseline deliberately on the canonical machine instead.
The 24 behavioral keyboard/layout/tabs tests are kept as-is.

AGENTS.md trimmed to a pointer at CLAUDE.md (review should-fix) to
avoid drift between duplicated guidance.

Also dropped a dead getAttachmentHistoryForPersist stub (codex-branch
residue — no such method exists in src/).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/session-resize-arbitration.test.ts

@@ -17,21 +17,96 @@ function attachFakePty(session: Session, cols = 160, rows = 48) {
 }
 
 describe('Session resize arbitration', () => {
-  it('ignores mobile resizes that would shrink a wider desktop PTY', () => {
+  it('lets a mobile-only session shrink below the spawn default (no desktop connected)', () => {
     const session = new Session({ workingDir: '/tmp', mode: 'shell' });
     const resize = attachFakePty(session, 160, 48);
 
     session.resize(48, 28, { viewportType: 'mobile' });
 
-    expect(resize).not.toHaveBeenCalled();
+    expect(resize).toHaveBeenCalledWith(48, 28);
   });
 
-  it('allows desktop resizes to change the shared PTY dimensions', () => {
+  it('lets a mobile-only session shrink rows only', () => {
     const session = new Session({ workingDir: '/tmp', mode: 'shell' });
     const resize = attachFakePty(session, 160, 48);
 
+    session.resize(160, 28, { viewportType: 'mobile' });
+
+    expect(resize).toHaveBeenCalledWith(160, 28);
+  });
+
+  it('lets a mobile-only session re-grow after shrinking', () => {
+    const session = new Session({ workingDir: '/tmp', mode: 'shell' });
+    const resize = attachFakePty(session, 160, 48);
+
+    session.resize(48, 28, { viewportType: 'mobile' });
+    session.resize(80, 36, { viewportType: 'tablet' });
+
+    expect(resize).toHaveBeenNthCalledWith(1, 48, 28);
+    expect(resize).toHaveBeenNthCalledWith(2, 80, 36);
+  });
+
+  it('ignores mobile resizes while a desktop connection holds a sizing claim', () => {
+    const session = new Session({ workingDir: '/tmp', mode: 'shell' });
+    const resize = attachFakePty(session, 160, 48);
+    const desktop = Symbol('desktop-conn');
+
+    session.claimDesktopSizing(desktop);
+    session.resize(48, 28, { viewportType: 'mobile' });
+    // Grow is ignored too — it would reflow the desktop view just the same.
+    session.resize(200, 60, { viewportType: 'tablet' });
+
+    expect(resize).not.toHaveBeenCalled();
+  });
+
+  it('always applies desktop resizes, claim or not', () => {
+    const session = new Session({ workingDir: '/tmp', mode: 'shell' });
+    const resize = attachFakePty(session, 160, 48);
+
+    session.claimDesktopSizing(Symbol('desktop-conn'));
     session.resize(120, 40, { viewportType: 'desktop' });
 
     expect(resize).toHaveBeenCalledWith(120, 40);
   });
+
+  it('restores mobile control once the desktop claim is released', () => {
+    const session = new Session({ workingDir: '/tmp', mode: 'shell' });
+    const resize = attachFakePty(session, 160, 48);
+    const desktop = Symbol('desktop-conn');
+
+    session.claimDesktopSizing(desktop);
+    session.resize(48, 28, { viewportType: 'mobile' });
+    expect(resize).not.toHaveBeenCalled();
+
+    session.releaseDesktopSizing(desktop);
+    session.resize(48, 28, { viewportType: 'mobile' });
+    expect(resize).toHaveBeenCalledWith(48, 28);
+  });
+
+  it('keeps ignoring mobile resizes until every desktop claim is released', () => {
+    const session = new Session({ workingDir: '/tmp', mode: 'shell' });
+    const resize = attachFakePty(session, 160, 48);
+    const desktopA = Symbol('desktop-a');
+    const desktopB = Symbol('desktop-b');
+
+    session.claimDesktopSizing(desktopA);
+    session.claimDesktopSizing(desktopB);
+    session.releaseDesktopSizing(desktopA);
+    session.resize(48, 28, { viewportType: 'mobile' });
+    expect(resize).not.toHaveBeenCalled();
+
+    session.releaseDesktopSizing(desktopB);
+    session.resize(48, 28, { viewportType: 'mobile' });
+    expect(resize).toHaveBeenCalledWith(48, 28);
+  });
+
+  it('applies untyped (legacy/API) resizes regardless of claims', () => {
+    const session = new Session({ workingDir: '/tmp', mode: 'shell' });
+    const resize = attachFakePty(session, 160, 48);
+
+    session.claimDesktopSizing(Symbol('desktop-conn'));
+    session.resize(100, 30);
+
+    expect(resize).toHaveBeenCalledWith(100, 30);
+  });
 });