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/inflection.yaml

@@ -16,6 +16,6 @@ patterns:
 verify:
   method: GET
   url: ""
-  headers: {}
-  valid_status: []
-  invalid_status: []
+  success_codes: [200]
+  failure_codes: [401, 403]
+  rate_limit_codes: [429]