What does this PR do?

Makes the Hermes Agent Web UI responsive and usable on mobile devices. Currently the layout breaks on screens under ~640px — nav text overflows, session cards crumble, and the ConfigPage sidebar doesn't collapse.

All changes use Tailwind's sm: breakpoint prefix with no logic changes.

Related Issue

N/A

Type of Change

• ✨ New feature (non-breaking change that adds functionality)

Changes Made

• web/src/App.tsx — Nav shows icons only on mobile (icon+label on sm+), brand abbreviated to "H A", reduced content padding, footer font sizes scaled down
• web/src/index.css — Add overflow-x: hidden to html, body to prevent horizontal scroll
• web/src/components/ui/card.tsx — Add overflow-hidden w-full to prevent content bleed past card borders
• web/src/pages/StatusPage.tsx — Session cards stack vertically on mobile, truncate overflow text, strip model namespace (xiaomi/mimo-v2-pro → mimo-v2-pro), add w-full to inner containers
• web/src/pages/ConfigPage.tsx — Sidebar becomes horizontal scrollable category pills on mobile instead of fixed left column, search input hidden on mobile
• web/src/pages/SessionsPage.tsx — Title + search bar stack vertically on mobile, search goes full-width on small screens

How to Test

1. cd web && npm install && npm run build — confirm build succeeds
2. Open the Web UI on a mobile device or in Chrome DevTools mobile emulation (375px width)
3. Verify: nav shows icons only, session cards don't overflow, content fits screen width
4. Resize to desktop (sm+) — layout should match existing behavior

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature
• I've run npm run build and the build succeeds
• I've tested on my platform: Android (Brave browser), iOS not tested

Documentation & Housekeeping

• I've updated relevant documentation — or N/A
• I've updated cli-config.yaml.example — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md — or N/A
• I've considered cross-platform impact — N/A (pure CSS/Tailwind, no platform-specific code)
• I've updated tool descriptions/schemas — or N/A

Screenshots

Before: session cards overflow horizontally, nav text crowds on mobile.
After: clean icon-only nav, cards stack vertically with proper truncation, content fits screen width.