feat(pilot): pydantic schemas for inline origin + script PATCH

- ScriptBuilderCreateRequest gains origin ('standalone' | 'pilot_inline')
  and optional ai_session_id. Handler-side validation (next task) enforces
  pilot_inline ⇒ ai_session_id required + owned by caller.
- SessionSuggestedFixScriptRequest added for the new PATCH /script
  endpoint (Phase 9 Task 6).

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

backend/app/schemas/session_suggested_fix.py

@@ -114,6 +114,17 @@ class SessionSuggestedFixOutcomeRequest(BaseModel):
     notes: str | None = Field(None, max_length=500)
 
 
+class SessionSuggestedFixScriptRequest(BaseModel):
+    """Engineer-submitted drafted script for a suggested fix.
+
+    Called when the inline Script Builder tab's Submit action fires. The
+    fix must be non-terminal (still proposed/applied_partial). Setting
+    the script does NOT stamp applied_at — a draft is not an application.
+    """
+    ai_drafted_script: str = Field(..., min_length=1, max_length=50_000)
+    ai_drafted_parameters: dict[str, Any] | None = None
+
+
 # ── Resolution note preview ────────────────────────────────────────────────
 
 class ResolutionNotePreviewResponse(BaseModel):