feat(05-04): extend Tier 1 provider verify specs

- 12 Tier 1 providers now carry success_codes, failure_codes, rate_limit_codes
- {{KEY}} template in headers or URL (double-brace canonical form)
- metadata_paths added where provider APIs return useful metadata
- Anthropic switched to POST /v1/messages with minimal body
- Perplexity gains JSON body, content-type header
- Inflection verify URL left empty (no public endpoint)
- Dual-location sync preserved: providers/ mirrors pkg/providers/definitions/

pkg/providers/definitions/google-ai.yaml

@@ -14,7 +14,9 @@ patterns:
     confidence: high
 verify:
   method: GET
-  url: https://generativelanguage.googleapis.com/v1/models?key={KEY}
-  headers: {}
-  valid_status: [200]
-  invalid_status: [400, 401, 403]
+  url: https://generativelanguage.googleapis.com/v1/models?key={{KEY}}
+  success_codes: [200]
+  failure_codes: [400, 401, 403]
+  rate_limit_codes: [429]
+  metadata_paths:
+    first_model: "models.0.name"