feat(llm): add GitHub Copilot as LLM provider (#1512)

* Add github copilot as LLM provider.

* Fix Copilot in Openclaw

* security: harden Copilot OAuth token handling

C1: Use secrecy::SecretString for oauth_token and cached session token
    in CopilotTokenManager/CachedCopilotToken. Expose only at HTTP
    header injection point via .expose_secret().

C2: Document risks of hardcoded VS Code OAuth client ID and editor
    identity headers (ToS, rotation, staleness). Remove the unreliable
    paste-token setup path (setup_github_copilot_manual_token).

C3: Fix TOCTOU race in get_token() — re-check token validity after
    acquiring write lock so concurrent callers don't all perform
    redundant token exchanges.

I1: Remove dead empty else {} block in get_token().

I2: Map 401 responses to LlmError::AuthFailed instead of RequestFailed
    so retry/circuit-breaker logic handles auth failures correctly.

I3: Replace prepare_github_copilot_setup() with call to existing
    set_llm_backend_preserving_model() helper to avoid logic drift.

I4: Add unit tests for CopilotTokenManager (caching, invalidation,
    expiry/buffer behavior), poll response parsing (all OAuth device
    flow states), and DeviceCodeResponse/CopilotTokenResponse deserialization.

Co-authored-by: Copilot <[email protected]>

* fix: address review feedback and code improvements (takeover #1202)

- Fix ContentPart::Text being silently dropped in convert_messages
- Replace custom truncate_for_error with crate::util::floor_char_boundary
- Fix CLAUDE.md: accurately describe dedicated provider (not "OpenAI-compatible path")
- Fix "Github" -> "GitHub" capitalization in READMEs
- Add manual token paste option to setup wizard (not just device login)
- Fix missing extension_manager field in EngineContext (merge fixup)
- cargo fmt applied

Co-Authored-By: fallenwood <[email protected]>
Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: address PR review feedback for GitHub Copilot provider

- Plumb request_timeout_secs into GithubCopilotProvider (was hardcoded 120s)
- Forward stop_sequences to Copilot API via OpenAI `stop` field
- Skip empty text part in multimodal message conversion
- Improve paste-token wizard hint with specific file path guidance

Co-Authored-By: fallenwood <[email protected]>
Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: 401 retry, retryable token exchange errors, shared retry-after parsing

- Retry once inline on 401 after token invalidation (was returning
  AuthFailed immediately, guaranteeing user-visible failure)
- Map token exchange failures to RequestFailed (retryable) instead of
  AuthFailed (non-retryable by RetryProvider)
- Use shared crate::llm::retry::parse_retry_after for HTTP-date support
  and safe 60s default
- Improve paste-token wizard hint: mention `gh auth token` as primary source

Co-Authored-By: fallenwood <[email protected]>
Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: 401 retry error mapping, retry status logging, token whitespace safety

- Map 401 retry get_token() failure to RequestFailed (retryable),
  consistent with initial token acquisition path
- Log retry response status before returning AuthFailed
- Trim oauth_token in exchange_copilot_token to prevent header panics
  from whitespace in env vars

Co-Authored-By: fallenwood <[email protected]>
Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

---------

Co-authored-by: Fallenwood <[email protected]>
Co-authored-by: Copilot <[email protected]>
Co-authored-by: fallenwood <[email protected]>
Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

docs/LLM_PROVIDERS.md

@@ -17,6 +17,7 @@ configurations.
 | Yandex AI Studio | `yandex` | `YANDEX_API_KEY` | YandexGPT models |
 | MiniMax | `minimax` | `MINIMAX_API_KEY` | MiniMax-M2.7 models |
 | Cloudflare Workers AI | `cloudflare` | `CLOUDFLARE_API_KEY` | Access to Workers AI |
+| GitHub Copilot | `github_copilot` | `GITHUB_COPILOT_TOKEN` | Multi-models |
 | Ollama | `ollama` | No | Local inference |
 | AWS Bedrock | `bedrock` | AWS credentials | Native Converse API |
 | OpenRouter | `openai_compatible` | `LLM_API_KEY` | 300+ models |
@@ -61,6 +62,34 @@ Popular models: `gpt-4o`, `gpt-4o-mini`, `o3-mini`
 
 ---
 
+## GitHub Copilot
+
+GitHub Copilot exposes chat endpoint at
+`https://api.githubcopilot.com`. IronClaw uses that endpoint directly through the
+built-in `github_copilot` provider.
+
+```env
+LLM_BACKEND=github_copilot
+GITHUB_COPILOT_TOKEN=gho_...
+GITHUB_COPILOT_MODEL=gpt-4o
+# Optional advanced headers if your setup needs them:
+# GITHUB_COPILOT_EXTRA_HEADERS=Copilot-Integration-Id:vscode-chat
+```
+
+`ironclaw onboard` can acquire this token for you using GitHub device login. If you
+already signed into Copilot through VS Code or a JetBrains IDE, you can also reuse
+the `oauth_token` stored in `~/.config/github-copilot/apps.json`. If you prefer,
+`LLM_BACKEND=github-copilot` also works as an alias.
+
+Popular models vary by subscription, but `gpt-4o` is a safe default. IronClaw keeps
+model entry manual for this provider because GitHub Copilot model listing may require
+extra integration headers on some clients. IronClaw automatically injects the standard
+VS Code identity headers (`User-Agent`, `Editor-Version`, `Editor-Plugin-Version`,
+`Copilot-Integration-Id`) and lets you override them with
+`GITHUB_COPILOT_EXTRA_HEADERS`.
+
+---
+
 ## Ollama (local)
 
 Install Ollama from [ollama.com](https://ollama.com), pull a model, then: