fix(pilot): persist AI-proposal rejection + clear on outcome write

Issue #3 from phase-8-review-issues.md. 'Not yet' on the AI-confirming
banner was a local-state hide; the proposal re-surfaced on the next
refreshSessionDerived call.

Two-part fix:
- PATCH /outcome now clears ai_outcome_proposal on any terminal action
  (engineer has taken a decision; stale AI proposal is moot).
- New DELETE /ai-sessions/:sid/suggested-fixes/:fid/ai-outcome-proposal
  endpoint for explicit 'Not yet' rejection. Does not touch status
  or state_version — pure UI state.

Frontend handleRejectAIProposal now calls the DELETE and setActiveFix
with the server response.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/api/endpoints/session_suggested_fixes.py

@@ -338,6 +338,9 @@ async def patch_suggested_fix_outcome(
     if fix.applied_at is None and body.outcome != "dismissed":
         fix.applied_at = now
 
+    # Clear any pending AI outcome proposal — engineer has taken a terminal action.
+    fix.ai_outcome_proposal = None
+
     # Outcome changes the bundle that resolution-note/escalation-package
     # previews see, so bump state_version inside the same transaction —
     # mirrors the pattern in record_decision above.
@@ -352,6 +355,48 @@ async def patch_suggested_fix_outcome(
     return SessionSuggestedFixResponse.model_validate(fix)
 
 
+# ── Suggested fix: clear AI outcome proposal ("Not yet") ─────────────────────
+
+@router.delete(
+    "/suggested-fixes/{fix_id}/ai-outcome-proposal",
+    response_model=SessionSuggestedFixResponse,
+)
+async def clear_ai_outcome_proposal(
+    session_id: UUID,
+    fix_id: UUID,
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    db: Annotated[AsyncSession, Depends(get_db)],
+    _: None = Depends(require_engineer_or_admin),
+) -> SessionSuggestedFixResponse:
+    """Explicitly dismiss the AI-proposed outcome banner ("Not yet").
+
+    Clears `ai_outcome_proposal` without touching status or state_version
+    (this is pure UI state, not outcome data). Idempotent: returns 200 even
+    when the field is already null. After this call the banner will not
+    re-surface on the next refreshSessionDerived unless the AI emits a new
+    proposal.
+    """
+    await _load_session_or_404(db, session_id)
+
+    result = await db.execute(
+        select(SessionSuggestedFix).where(
+            SessionSuggestedFix.id == fix_id,
+            SessionSuggestedFix.session_id == session_id,
+        )
+    )
+    fix = result.scalar_one_or_none()
+    if fix is None:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Suggested fix not found"
+        )
+
+    fix.ai_outcome_proposal = None
+
+    await db.commit()
+    await db.refresh(fix)
+    return SessionSuggestedFixResponse.model_validate(fix)
+
+
 async def _summarize_session_for_extraction(
     db: AsyncSession, session_id: UUID,
 ) -> str:

backend/tests/test_fix_outcome_endpoint.py

@@ -437,3 +437,100 @@ async def test_apply_rejects_dismissed(
         headers=auth_headers,
     )
     assert r.status_code == 409, r.text
+
+
+# ── AI outcome proposal: clear / reject ───────────────────────────────────────
+
+async def _make_session_with_fix_and_proposal(test_db, user) -> tuple[str, str]:
+    """Create an AISession + fix with a populated ai_outcome_proposal."""
+    from uuid import UUID as _UUID
+    session = AISession(
+        user_id=user["user_data"]["id"],
+        account_id=user["user_data"]["account_id"],
+        session_type="chat",
+        intake_type="free_text",
+        intake_content={"text": "proposal clear test"},
+        status="active",
+        confidence_tier="discovery",
+        conversation_messages=[],
+    )
+    test_db.add(session)
+    await test_db.flush()
+
+    fix = SessionSuggestedFix(
+        session_id=session.id,
+        account_id=session.account_id,
+        title="Flush DNS cache",
+        description="Run ipconfig /flushdns on the affected host.",
+        confidence_pct=74,
+        ai_outcome_proposal={"fix_id": str(session.id), "outcome": "success", "reason": "User confirmed resolved"},
+    )
+    test_db.add(fix)
+    await test_db.commit()
+    await test_db.refresh(fix)
+
+    return str(session.id), str(fix.id)
+
+
+@pytest.mark.asyncio
+async def test_outcome_patch_clears_ai_proposal(
+    client: AsyncClient, test_user, auth_headers, test_db
+):
+    """PATCH /outcome clears ai_outcome_proposal regardless of which outcome is written."""
+    session_id, fix_id = await _make_session_with_fix_and_proposal(test_db, test_user)
+
+    # Verify the proposal is set before the patch.
+    from uuid import UUID
+    result = await test_db.execute(
+        select(SessionSuggestedFix).where(SessionSuggestedFix.id == UUID(fix_id))
+    )
+    fix_before = result.scalar_one()
+    assert fix_before.ai_outcome_proposal is not None
+
+    r = await client.patch(
+        f"/api/v1/ai-sessions/{session_id}/suggested-fixes/{fix_id}/outcome",
+        headers=auth_headers,
+        json={"outcome": "applied_success"},
+    )
+    assert r.status_code == 200, r.text
+    body = r.json()
+    assert body["ai_outcome_proposal"] is None, (
+        "PATCH /outcome must clear ai_outcome_proposal on any terminal action"
+    )
+
+
+@pytest.mark.asyncio
+async def test_delete_ai_proposal_clears_field(
+    client: AsyncClient, test_user, auth_headers, test_db
+):
+    """DELETE /ai-outcome-proposal clears the field without changing status."""
+    session_id, fix_id = await _make_session_with_fix_and_proposal(test_db, test_user)
+
+    r = await client.delete(
+        f"/api/v1/ai-sessions/{session_id}/suggested-fixes/{fix_id}/ai-outcome-proposal",
+        headers=auth_headers,
+    )
+    assert r.status_code == 200, r.text
+    body = r.json()
+    assert body["ai_outcome_proposal"] is None, (
+        "DELETE /ai-outcome-proposal must clear the field"
+    )
+    assert body["status"] == "proposed", (
+        "DELETE /ai-outcome-proposal must not change fix status"
+    )
+
+
+@pytest.mark.asyncio
+async def test_delete_ai_proposal_when_none_is_idempotent(
+    client: AsyncClient, test_user, auth_headers, test_db
+):
+    """DELETE /ai-outcome-proposal returns 200 even when the field is already null."""
+    session_id, fix_id = await _make_session_with_fix(test_db, test_user)
+
+    # Fix created by _make_session_with_fix has ai_outcome_proposal=None.
+    r = await client.delete(
+        f"/api/v1/ai-sessions/{session_id}/suggested-fixes/{fix_id}/ai-outcome-proposal",
+        headers=auth_headers,
+    )
+    assert r.status_code == 200, r.text
+    assert r.json()["ai_outcome_proposal"] is None