feat(03-02): add voice and image/video Tier 3 providers

- Deepgram (hex40, low confidence)
- ElevenLabs (hex32, XI_API_KEY header)
- Stability AI (sk- prefix, medium confidence)
- Runway (keyword-only)
- Midjourney (keyword-only, no official API)

Completes PROV-03: 12 Tier 3 Specialized providers (with pre-existing huggingface).

pkg/providers/definitions/runway.yaml

@@ -0,0 +1,19 @@
+format_version: 1
+name: runway
+display_name: Runway
+tier: 3
+last_verified: "2026-04-05"
+keywords:
+  - "runway"
+  - "runwayml"
+  - "RUNWAY_API_KEY"
+  - "RUNWAYML_API_SECRET"
+  - "api.runwayml.com"
+  - "dev.runwayml.com"
+verify:
+  method: GET
+  url: https://api.dev.runwayml.com/v1/tasks
+  headers:
+    Authorization: "Bearer {KEY}"
+  valid_status: [200, 400]
+  invalid_status: [401, 403]