fix: optimize mobile remote control flows

[joeynyc]

Outcome

Makes Grok UI practical and safer on phones across 360px–430px widths: a compact five-item bottom navigation, accessible overflow drawer, responsive Fleet session cards, reachable remote chat and permission controls, safe-area handling, and robust focus restoration for touch, keyboard, Chromium, and Safari/WebKit.

The remote-control protocol and trust boundaries are unchanged. Commands remain authenticated, idempotent, expiring, reconnect-safe, and host-controlled.

Verification

• npm run verify — 87 unit/server tests, type checks, production build, release check
• Relevant automated tests added or updated
• Desktop behavior checked
• Mobile behavior checked at 360px, 390px, and 430px
• Chromium: 24/24 Playwright scenarios
• WebKit/Safari engine: 24/24 Playwright scenarios
• Packaged-install and browser/security smoke passed
• 75-second control/fleet reconnect soak passed
• Production dependency audit: 0 vulnerabilities
• Grok CLI and Claude Code CLI independent closure reviews: PASS
• No credentials, prompts, private source, personal names, local paths, or IP addresses added
• Fleet changes preserve authenticated, bounded remote access
• Fleet changes cover compatibility, failure, freshness, and reconnect states

Safety and accessibility

• Workbench and mobile navigation focus is contained and restored to the correct opener.
• Invisible scrims are excluded from the Tab order.
• Background navigation is suspended while dialogs are active.
• WebKit CI coverage is now required alongside Chromium.
• Long runtime paths are ellipsized to prevent Safari-only horizontal overflow.

Screenshots

Manual mobile visual QA was completed with sanitized fixture data; no screenshots containing local paths or private data are attached.