Fix: restore home ambient suggestions

[xIGBClutchIx]

Summary

This restores ambient suggestions on the New chat view in Pocodex by implementing the missing vscode://codex/ambient-suggestions bridge contract and the related ambient-suggestion routes the current Codex bundle now calls.

What changed

• add app-server bridge handlers for ambient-suggestions, ambient-suggestions-refresh, ambient-suggestions-generation-statuses, and ambient-suggestion-set-status
• return the file.currentSuggestionIds and file.suggestions payload shape the current Codex bundle expects, backed by a small in-memory ambient suggestion store
• keep refresh and generation-status requests on the supported host fetch path instead of falling through to the generic unsupported-route response
• add focused regression coverage for ambient suggestion fetch, status update, refresh, and generation-status flows in test/app-server-bridge-host-data.test.ts

Root cause

• the current Codex bundle loads home-view ambient suggestions through vscode://codex/ambient-suggestions
• Pocodex did not implement that host fetch route or its related ambient-suggestion helpers, so those requests fell through to the default 501 unsupported path
• once that bridge contract failed, the New chat surface could not load ambient suggestion data and surfaced the route failure instead of normal suggestion behavior

Impact

• New chat no longer fails on the missing ambient-suggestions host fetch path
• ambient suggestion consumers now receive the payload shape they expect, including a safe empty-state response and working refresh/status endpoints
• focused regression coverage now protects this host bridge contract from falling back to unsupported-route behavior again

Validation

• pnpm run check:commit
• pnpm vitest run test/app-server-bridge-host-data.test.ts
• pnpm exec tsx src/cli.ts --dev --listen 127.0.0.1:8793
• live local verification on http://127.0.0.1:8793/ that New chat rendered What should we work on in pocodex? and did not show Unsupported Codex host fetch URL: vscode://codex/ambient-suggestions