docs: add docs for Copilot device flow

docs/providers/github-copilot.md

@@ -0,0 +1,49 @@
+---
+summary: "Sign in to GitHub Copilot from Clawdbot using the device flow"
+read_when:
+  - You want to use GitHub Copilot as a model provider
+  - You need the `clawdbot models auth login-github-copilot` flow
+---
+# Github Copilot
+
+Use GitHub Copilot as a model provider (`github-copilot`). The login command runs
+the GitHub device flow, saves an auth profile, and updates your config to use that
+profile.
+
+## CLI setup
+
+```bash
+clawdbot models auth login-github-copilot
+```
+
+You'll be prompted to visit a URL and enter a one-time code. Keep the terminal
+open until it completes.
+
+### Optional flags
+
+```bash
+clawdbot models auth login-github-copilot --profile-id github-copilot:work
+clawdbot models auth login-github-copilot --yes
+```
+
+## Set a default model
+
+```bash
+clawdbot models set github-copilot/gpt-4o
+```
+
+### Config snippet
+
+```json5
+{
+  agents: { defaults: { model: { primary: "github-copilot/gpt-4o" } } }
+}
+```
+
+## Notes
+
+- Requires an interactive TTY; run it directly in a terminal.
+- Copilot model availability depends on your plan; if a model is rejected, try
+  another ID (for example `github-copilot/gpt-4.1`).
+- The login stores a GitHub token in the auth profile store and exchanges it for a
+  Copilot API token when Clawdbot runs.