feat: Code Mode — the registry's mode config, the SDK codegen, and the run_code bridge

The dsh-tools half of the Code Mode RFC (its fourth, final change): the
registry gains its first config — mode: native | code | both — and OWNS how
its tools reach the model. 'code' contributes exactly one wire tool,
run_code, plus a lazy tools:sdk prompt section declaring every other tool
as a generated TypeScript API (jsonSchemaToTs: total over the defineTool
subset, unknown degradation, lexicographic byte-identical rendering);
'both' ships both representations; 'native' is byte-for-byte the old
behavior. Non-native modes fail every assembly loudly without a
typescript-language ctx.codeRuntime.

run_code's dispatch bridge: JSON-normalizes each binding argument before
dispatch (what dispatches is what the tool/code-dispatch event logs — the
append can never fail on payload shape; BigInt/circulars reject that one
call), serializes all program tool calls through a per-run queue (even
Promise.all — no concurrency-safety metadata yet), routes every sub-call
through tools/pre-execute → tools/post-execute (a deny rejects the
program-side promise), drops sub-call additionalContext (no safe outlet
mid-run; pinned), owns a run-scoped abort that follows the outer signal in
and fires on settlement (in-flight sub-dispatch aborted, queued abandoned,
queue drained before returning), and converts a failed run into
CodeRunFailedError → a structured isError carrying kind + captured logs.
tool/code-dispatch joins SessionEventMap by declaration merging (log-only;
deriveMessages ignores it).

The composed surface: the tools config forwards through agent-core and
both app packages; examples/code-agent + demo:code run the worker runtime
under mode code (keyless boot smoke + a with-key e2e proving the collapsed
[run_code] header, the dispatch events, and the file the program wrote);
two new snapshot scenarios (code-mode-turn, both-mode-turn) record the SDK
section, collapsed header, dispatch events, and result card — each its own
header-pinning class (the harness gains per-scenario config overlays and
per-class pins). Catalogs, graphs, cookbook, hooks-bridge notes, and the
RFC (moved to implemented/, restructured to decision-era headings) updated
in the same change.

docs/cookbook/adding-a-tool.md

@@ -49,6 +49,10 @@ Follow tool-bash's background pattern: a `run_in_background` flag returns a task
 
 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).