fix(ai): MockAIProvider DEFAULT_RESPONSE conforms to v1.4.15 strict schema

Phase D senior-dev review HIGH H4: the mock's default response carried
the legacy v1.4.14 rich shape (classification, findings, correlations,
dataQuality, disclaimer). The v1.4.15 strict schema requires
{summary, recommendations, citations, warnings}. The default passed
only because of `aiInsightResponseSchema.passthrough()`; once v1.4.16
retires the passthrough, every test using the default mock would
silently start failing schema validation before its asserts ran.

Switch to a strict-schema-conformant default. Tests needing the
legacy shape opt in via `responses: [...]`.

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

src/lib/ai/mock-client.ts

@@ -39,14 +39,13 @@ export interface MockAIProviderOptions {
   tokensUsed?: number | number[] | null;
 }
 
+// Conforms to v1.4.15 strict `aiInsightResponseSchema`. Tests that need
+// the legacy v1.4.14 rich shape opt in via `responses: [...]`.
 const DEFAULT_RESPONSE = JSON.stringify({
   summary: "mock",
-  classification: "gut",
-  findings: [],
-  correlations: [],
   recommendations: [],
-  dataQuality: { coverage: "mock", gaps: [], confidence: "mittel" },
+  citations: [],
-  disclaimer: "mock disclaimer",
+  warnings: [],
 });
 
 export class MockAIProvider implements AIProvider {