feat(codex-local): add fast mode support

docs/adapters/codex-local.md

@@ -20,6 +20,7 @@ The `codex_local` adapter runs OpenAI's Codex CLI locally. It supports session p
 | `env` | object | No | Environment variables (supports secret refs) |
 | `timeoutSec` | number | No | Process timeout (0 = no timeout) |
 | `graceSec` | number | No | Grace period before force-kill |
+| `fastMode` | boolean | No | Enables Codex Fast mode. Currently supported on `gpt-5.4` only and burns credits faster |
 | `dangerouslyBypassApprovalsAndSandbox` | boolean | No | Skip safety checks (dev only) |
 
 ## Session Persistence
@@ -30,6 +31,16 @@ Codex uses `previous_response_id` for session continuity. The adapter serializes
 
 The adapter symlinks Paperclip skills into the global Codex skills directory (`~/.codex/skills`). Existing user skills are not overwritten.
 
+## Fast Mode
+
+When `fastMode` is enabled, Paperclip adds Codex config overrides equivalent to:
+
+```sh
+-c 'service_tier="fast"' -c 'features.fast_mode=true'
+```
+
+Paperclip currently applies that only when the selected model is `gpt-5.4`. On other models, the toggle is preserved in config but ignored at execution time to avoid unsupported runs.
+
 When Paperclip is running inside a managed worktree instance (`PAPERCLIP_IN_WORKTREE=true`), the adapter instead uses a worktree-isolated `CODEX_HOME` under the Paperclip instance so Codex skills, sessions, logs, and other runtime state do not leak across checkouts. It seeds that isolated home from the user's main Codex home for shared auth/config continuity.
 
 For manual local CLI usage outside heartbeat runs (for example running as `codexcoder` directly), use: