Merge remote-tracking branch 'origin/master' into codex/rfc-subagent-background-tasks

Adopts #211 (Code Mode tools: run_code + the code/both-mode snapshot
scenarios). Tool-catalog expectations take the union (run_code +
task_*); the two new pinsHeader fixtures (code-mode-turn,
both-mode-turn) were recorded on master without the task runtime, so
they are re-pinned KEYLESSLY by replaying their recorded chunks against
the merged tree (same procedure as text-turn) — the fixture diff is
exactly the header delta: task tool schemas, the tool:tasks prompt
section, and the bash background wording.

docs/cookbook/adding-a-tool.md

@@ -47,6 +47,10 @@ Hand long-running work to the shared task runtime instead of inventing a task pr
 
 Prefer not to build policy into the tool. The seam is the `tools/pre-execute` gate (deny/ask — see the permission-gate example in [extension-cookbook.md](./extension-cookbook.md)) and the `tools/post-execute` inspect/transform seam, or a sandboxing implementation behind the tool's executor seam.
 
+## Code Mode reaches your tool for free
+
+Under the registry's non-native `mode` ([Code Mode](../../packages/core/tools/README.md)), a registered tool is ALSO callable from a `run_code` program as `await tools.<name>(args)` — nothing to add. The generated SDK declares your parameters from the same JSON Schema `defineTool` emits (constructs outside that subset degrade to `unknown`), each program call re-enters `execute()` through both waterfalls, and a failed call rejects the program-side promise with your error text. Two consequences worth designing for: your `description` and parameter `description`s become JSDoc a model reads while WRITING CODE, and non-text result blocks reach programs as placeholders (text is the lingua franca of the bridge).
+
 ## How your tool renders in an editor (ACP presentation)
 
 Your tool's `execute` returns model-facing content; its **editor card** is a separate, optional concern you declare with two pure display methods on the `defineTool` options. Design this alongside `execute`, not after — an editor (Zed, over the ACP bridge) shows the card, and a tool with no presentation falls back to a bland generic card (title = tool name, raw args as input).