feat(03-04): add GitHub Copilot, Cursor, Tabnine, Codeium, Sourcegraph providers

- GitHub Copilot with ghu_/gho_ token patterns
- Sourcegraph Cody with documented sgp_ high-confidence pattern
- Cursor, Tabnine, Codeium as keyword-only (no documented formats)

providers/tabnine.yaml

@@ -0,0 +1,16 @@
+format_version: 1
+name: tabnine
+display_name: Tabnine
+tier: 7
+last_verified: "2026-04-05"
+keywords:
+  - "tabnine"
+  - "TABNINE_API_KEY"
+  - "api.tabnine.com"
+  - "tabnine-pro"
+verify:
+  method: GET
+  url: ""
+  headers: {}
+  valid_status: []
+  invalid_status: []