docs: forbid improvised commit fallbacks when MCP commit exists (#260)

Document MCP-native gitea_commit_files as the only approved commit path when
gitea.repo.commit is allowed; ban WebFetch, Playwright, and manual base64
workarounds in runbooks and safety model. Add doc tests.

Closes #260.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

docs/llm-workflow-runbooks.md

@@ -370,6 +370,36 @@ git branch -d fix/issue-123-example
 All three helpers accept `--dry-run` to print the exact commands/paths without
 touching anything.
 
+### MCP-native commit path (#260)
+
+When the active author profile allows **`gitea.repo.commit`** and
+**`gitea_commit_files`** is visible in the client, that is the **only** approved
+path for committing files to the tracked repository. Do not improvise alternate
+encoding or transport when MCP commit is available.
+
+**Required before commit:**
+
+1. Call `gitea_resolve_task_capability` for `commit_files` or
+   `gitea_commit_files` and confirm `allowed_in_current_session` is true.
+2. Use `gitea_commit_files` with file payloads prepared in the author worktree.
+3. Stage only issue-scoped paths; never commit throwaway `_encode_*` /
+   `_emit_*` / `_inline_*` helpers.
+
+**Explicitly forbidden workarounds** when MCP commit is reachable:
+
+- `WebFetch` / HTTP calls to external decode sites (for example httpbin base64
+  endpoints)
+- Playwright or other browser automation to bypass MCP
+- Manual LLM-generated base64 pasted into ad-hoc scripts
+- Delegating commit authority to a subagent while the main session has
+  `gitea.repo.commit` on an author profile
+
+**If shell encoding is unavailable** (spawn failure, hung terminal) **and** MCP
+commit cannot run: **stop** with a recovery report. Mention restarting the
+session, clearing hung background terminals, switching to MCP-native commit, and
+the agent temp artifact cleanup checklist. Do **not** retry shell encoding in a
+loop and do **not** substitute WebFetch/Playwright/manual base64.
+
 ### Create an issue / child issues
 
 - **Profile:** issue-manager or author (any profile allowed to create issues).

docs/safety-model.md

@@ -28,3 +28,21 @@ Any mutating action (e.g., Gitea issue creation from GlitchTip, or Jenkins build
   No default profile carries trigger capability (#152 / mcp-control-plane #56).
 - **GlitchTip to Gitea issue filing** is a library-only orchestrator in
   mcp-control-plane (not on `glitchtip-mcp`). See #153 / mcp-control-plane #57.
+
+## 6. Agent Commit Path (no improvised fallbacks)
+
+When an author execution profile allows **`gitea.repo.commit`** and the
+**`gitea_commit_files`** tool is visible, agents must use that MCP path for
+repository commits. Fail closed instead of improvising alternate transports.
+
+Forbidden when MCP commit is available:
+
+- WebFetch or other HTTP calls to external base64/decode services
+- Playwright or browser automation used to work around MCP commit
+- Manual LLM-generated base64 embedded in throwaway scripts as the primary
+  commit transport
+
+If shell helpers are unavailable and MCP commit cannot run, stop with a recovery
+report (restart session, clear hung terminals, use MCP-native commit). See
+[`llm-workflow-runbooks.md`](llm-workflow-runbooks.md) § MCP-native commit path
+(#260) and agent temp artifact cleanup (#261).