feat(spill): bound the durable copy of Code Mode sub-dispatch results

New tools/code-dispatch-log waterfall (run via registry.shapeDispatchLog,
contained — a throwing listener falls back to the unshaped content) lets
listeners reshape the tool/code-dispatch event's content before the
bridge appends it. dsh-spill-policy registers a second arm sharing the
model-facing arm's exact replacement pipeline (same maxInlineBytes cap,
preview + locator, within-cap invariant, best-effort fallbacks), with
artifacts labeled dispatch under the sub-call id. The program's value is
untouched; read sub-calls ARE bounded (a log copy is not model context,
and read produces the biggest logs). Resolves the tools README's
uncapped-dispatch-log Known Limitation.

packages/spill/spill-policy/README.md

@@ -13,7 +13,7 @@ This plugin registers **no service** and owns no storage or preview mechanics: p
 ## Behavior
 
 1. Let the tool run (delegates via `next()`, so it bounds whatever a downstream hook accepted).
-2. Skip nested executions (`exec.parent` is present), accepted value replacements (the registry must revalidate and rerender them), `read` (avoids a `read → spill → read again` loop), and any non-`accept` decision (a `block`'s corrective feedback passes through).
+2. Skip nested executions (`exec.parent` is present — their DURABLE copy is bounded by the dispatch-log arm below), accepted value replacements (the registry must revalidate and rerender them), `read` (avoids a `read → spill → read again` loop), and any non-`accept` decision (a `block`'s corrective feedback passes through).
 3. Flatten the accepted content only when it is **plain text** (all `text` blocks); a result with any non-text block is left untouched.
 4. If its UTF-8 size is `≤ maxInlineBytes`, leave it unchanged.
 5. Otherwise save the full text and replace the result with a preview + this notice, sized so the whole replacement (preview + blank line + notice) stays within `maxInlineBytes` — the notice's byte cost is reserved out of the budget, so the preview shrinks to fit and the model-facing result never exceeds the cap:
@@ -28,6 +28,8 @@ This plugin registers **no service** and owns no storage or preview mechanics: p
 
 **Best-effort:** no session owner, no `ctx.spillStore` backend, or a `saveText` rejection ⇒ the policy logs a warning and returns the original result. A spill failure never turns a successful call into an `isError` or hides the inline result. A successful replacement changes only `content`; the canonical programmatic value is preserved.
 
+**The dispatch-log arm:** a second listener on `tools/code-dispatch-log` applies the same cap, replacement pipeline, and best-effort fallbacks to the DURABLE copy of each `run_code` sub-call result (artifact label `dispatch`, keyed by the sub-call id). The program's value is untouched — it already crossed the worker boundary whole — and `read` sub-calls are bounded too: a log copy is not model context, so the read-again loop cannot occur, and `read` is precisely the tool that produces huge logs ([rationale](../../../.agents/notes/implemented/feature/2026-07-26-code-dispatch-log-spill.md)).
+
 ## Scope
 
 The policy sees only the FINAL formatted surface result—not a tool's internal resource or canonical value. If a provider already truncated (e.g. `web-fetch-local.maxBodyChars`), the spill artifact holds the full formatted result the tool returned, not the full original source. Provider/resource caps stay mandatory and separate. `glob`/`grep` own item-level surface spill because their complete acquired values still exist before rendering; bash streams own acquisition-time spill. The generic policy prepends its waterfall listener, then delegates, so ordinary tool-owned asynchronous projections complete before generic byte bounding regardless of plugin load order. See the [tool output spill Agent Note](../../../.agents/notes/implemented/architecture/2026-07-08-tool-output-spill-files.md).