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/cursor.yaml

@@ -0,0 +1,17 @@
+format_version: 1
+name: cursor
+display_name: Cursor AI
+tier: 7
+last_verified: "2026-04-05"
+keywords:
+  - "cursor"
+  - "CURSOR_API_KEY"
+  - "cursor.sh"
+  - "cursor.com"
+  - "cursor-ide"
+verify:
+  method: GET
+  url: ""
+  headers: {}
+  valid_status: []
+  invalid_status: []