[Agent] Command palette hides search API failures

Agent brief

Category: ux | Severity: medium | Effort: S

Problem

Command palette search swallows API failures and shows empty results. Users think nothing matches when the API is down.

Repro

1. Block /api/search in devtools
2. Open palette, type query
3. Empty list with no error message

Files

• src/components/search/command-palette.tsx

Acceptance criteria

• Network/5xx shows "Search unavailable" inline
• Retry affordance or auto-retry once