fix(mobile): show GitHub profiles and align Harmony chat entry

[wgqqqqq]

Summary

Show GitHub usernames and avatars in HarmonyOS and mobile-web account surfaces instead of presenting a numeric account ID as the username. Label the immutable GitHub ID separately. Restore HarmonyOS's sidebar “Chat” action with remote mode selection matching mobile-web.

Type and Areas

Type: Bug fix / UI/UX

Areas: HarmonyOS mobile app, mobile web

Motivation / Impact

Already-signed-in users receive public GitHub profile metadata without signing in again. Profiles are cached by GitHub ID for 24 hours; unavailable metadata preserves the authenticated session and any cached profile. Profile requests never forward relay credentials, and account changes discard stale responses. Avatar load failures retain a fallback icon.

On HarmonyOS, Chat opens the harness selector for supported workspaces, creates an assistant session in assistant workspaces, and falls back to code session creation for older hosts. Disconnected or busy controllers cannot create a session. This continues to create sessions on the connected host; it does not restore phone-local chat.

Verification

• HarmonyOS LocalTest via hvigorw --mode module -p module=entry@default -p ohos.test.type=LocalTest test --no-daemon: 481 passed.
• HarmonyOS hvigorw --mode module -p product=default -p module=entry@default assembleHap --no-daemon: signed build passed; installed and launched on HUAWEI Mate X7.
• pnpm run harmony:architecture: passed.
• pnpm --dir src/mobile-web run test:account-login: 11 passed, including public profile validation, cache/offline behavior, and stale-account responses.
• pnpm --dir src/mobile-web run test:ui-components: 10 passed.
• pnpm --dir src/mobile-web run test:workspace-identity: 3 passed.
• pnpm --dir src/mobile-web run type-check: passed.
• pnpm run build:mobile-web: passed.
• git diff --check: passed.
• Codex in-app browser: visually checked the actual mobile-web settings component with a public sample profile at 390, 768, and 1280 px widths, including light/dark themes and live resizing.

Reviewer Notes

Existing account-session serialization and authorization identities are unchanged. Mobile-web CSP permits only the GitHub avatar host in addition to its existing image sources.

Remote-control session creation was exercised with a fake account transport in compact and wide HarmonyOS tests. A live GitHub-login/remote-device E2E flow and HarmonyOS visual/posture QA were not completed. Remote workspace, Peer Device Mode, and Detached Dispatch were not exercised by this change.

Local signing configuration and temporary preview files are excluded.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.