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/sourcegraph.yaml

@@ -0,0 +1,26 @@
+format_version: 1
+name: sourcegraph
+display_name: Sourcegraph Cody
+tier: 7
+last_verified: "2026-04-05"
+keywords:
+  - "sourcegraph"
+  - "cody"
+  - "SRC_ACCESS_TOKEN"
+  - "SOURCEGRAPH_TOKEN"
+  - "sourcegraph.com"
+  - "sgp_"
+patterns:
+  - regex: 'sgp_[A-Fa-f0-9]{16,}_[A-Fa-f0-9]{40}'
+    entropy_min: 4.0
+    confidence: high
+  - regex: 'sgp_[A-Fa-f0-9]{40}'
+    entropy_min: 4.0
+    confidence: medium
+verify:
+  method: GET
+  url: https://sourcegraph.com/.api/graphql
+  headers:
+    Authorization: "token {KEY}"
+  valid_status: [200]
+  invalid_status: [401, 403]