feat(pilot): PATCH /suggested-fixes/:id/outcome endpoint + tests

Records engineer-reported outcome (applied_success|applied_failed|
applied_partial|dismissed). Enforces transition rules (partial → success/
failed allowed; terminal outcomes return 409) and notes requirements
(applied_partial requires notes).

Sets verified_at on success/failure, stamps applied_at if not already
set (handles the case where the AI [FIX_OUTCOME] marker fires before
the engineer clicks Apply).

Also fixes pre-existing test-infrastructure bug: network_diagram.py used
bare string server_default="'[]'" for JSONB columns, which asyncpg
rejects during test schema creation. Changed to text("'[]'::jsonb") to
match the pattern used by script_template.py.

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

backend/app/schemas/session_suggested_fix.py

@@ -103,9 +103,11 @@ class SessionSuggestedFixOutcomeRequest(BaseModel):
     engineer took); outcome captures whether the fix actually worked.
 
     Allowed transitions:
-    - from `proposed`: any of applied_success | applied_failed | applied_partial | dismissed
-    - from `applied_partial`: applied_success | applied_failed  (partial is not terminal)
-    - from any terminal outcome: no change (server returns 409)
+    - from `proposed` or `applied_partial`: any outcome is valid
+      (partial is parked, not terminal — the engineer may update notes,
+      abandon via dismiss, or advance to success/failed)
+    - from any terminal outcome (`applied_success`, `applied_failed`,
+      `dismissed`): server returns 409
     """
     outcome: FixOutcome
     # Required for applied_partial, optional for applied_failed, ignored otherwise.