feat(search): add PostgreSQL FTS on AI sessions with Command Palette integration

- Migration: add generated tsvector column + GIN index on ai_sessions (problem_summary, resolution_summary, escalation_reason, problem_domain)
- Backend: wire FTS into list_sessions q param; add GET /ai-sessions/search endpoint returning AISessionSearchResult (registered before /{session_id} to avoid UUID routing conflict)
- Frontend: add AISessionSearchResult type, aiSessionsApi.search() method, and Command Palette group "FlowPilot Sessions" using Zap icon navigating to /pilot/:id

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/alembic/versions/dbf67047d4c8_add_full_text_search_vector_to_ai_.py

@@ -0,0 +1,43 @@
+"""add full-text search vector to ai_sessions
+
+Revision ID: dbf67047d4c8
+Revises: 49150866ae44
+Create Date: 2026-03-20 03:36:29.910843
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'dbf67047d4c8'
+down_revision: Union[str, None] = '49150866ae44'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Add generated tsvector column for full-text search
+    # Indexes: problem_summary, resolution_summary, escalation_reason, problem_domain
+    op.execute("""
+        ALTER TABLE ai_sessions ADD COLUMN IF NOT EXISTS search_vector tsvector
+        GENERATED ALWAYS AS (
+            to_tsvector('english',
+                coalesce(problem_summary, '') || ' ' ||
+                coalesce(resolution_summary, '') || ' ' ||
+                coalesce(escalation_reason, '') || ' ' ||
+                coalesce(problem_domain, ''))
+        ) STORED
+    """)
+    # Add GIN index for fast FTS lookups
+    op.execute("""
+        CREATE INDEX IF NOT EXISTS idx_ai_sessions_search
+        ON ai_sessions USING gin(search_vector)
+    """)
+
+
+def downgrade() -> None:
+    op.execute("DROP INDEX IF EXISTS idx_ai_sessions_search")
+    op.execute("ALTER TABLE ai_sessions DROP COLUMN IF EXISTS search_vector")

backend/app/api/endpoints/ai_sessions.py

@@ -16,7 +16,7 @@ from typing import Annotated, Optional
 from uuid import UUID
 
 from fastapi import APIRouter, Depends, HTTPException, Query, Request, status
-from sqlalchemy import or_, select, func
+from sqlalchemy import or_, select, func, text
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import selectinload
 
@@ -41,6 +41,7 @@ from app.schemas.ai_session import (
     AISessionSummary,
     AISessionDetail,
     AISessionStepResponse,
+    AISessionSearchResult,
     StepOptionSchema,
 )
 from app.services import flowpilot_engine
@@ -454,6 +455,44 @@ async def link_ticket_to_session(
     return detail
 
 
+# ── Search sessions (Command Palette) ──
+
+@router.get("/search", response_model=list[AISessionSearchResult])
+@limiter.limit("30/minute")
+async def search_sessions(
+    request: Request,
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    db: Annotated[AsyncSession, Depends(get_db)],
+    q: str = Query(..., min_length=2, max_length=200),
+    limit: int = Query(5, ge=1, le=20),
+):
+    """Search AI sessions by content using full-text search. Used by Command Palette."""
+    result = await db.execute(
+        select(AISession)
+        .where(
+            or_(
+                AISession.user_id == current_user.id,
+                AISession.account_id == current_user.account_id,
+            ),
+            text("ai_sessions.search_vector @@ plainto_tsquery('english', :q)"),
+        )
+        .params(q=q)
+        .order_by(AISession.created_at.desc())
+        .limit(limit)
+    )
+    sessions = result.scalars().all()
+    return [
+        AISessionSearchResult(
+            id=s.id,
+            problem_summary=s.problem_summary,
+            problem_domain=s.problem_domain,
+            status=s.status,
+            created_at=s.created_at,
+        )
+        for s in sessions
+    ]
+
+
 # ── List sessions ──
 
 @router.get("", response_model=list[AISessionSummary])
@@ -502,7 +541,10 @@ async def list_sessions(
         query = query.where(AISession.created_at >= date_from)
     if date_to:
         query = query.where(AISession.created_at <= date_to)
-    # TODO: Full-text search via q param — see Task 7
+    if q:
+        query = query.where(
+            text("ai_sessions.search_vector @@ plainto_tsquery('english', :q)")
+        ).params(q=q)
 
     result = await db.execute(query)
     sessions = result.scalars().all()

backend/app/schemas/ai_session.py

@@ -190,3 +190,14 @@ class AISessionDetail(AISessionSummary):
     steps: list[AISessionStepResponse] = []
 
     model_config = {"from_attributes": True}
+
+
+class AISessionSearchResult(BaseModel):
+    """Lightweight session result for Command Palette / autocomplete."""
+    id: UUID
+    problem_summary: str | None = None
+    problem_domain: str | None = None
+    status: str
+    created_at: datetime
+
+    model_config = {"from_attributes": True}