fix(tools): bound the shaped-append side channel; total error containment; recorded spill snapshot

Responding to ds-review-bot round 2 on #661:

- logWork is bounded: past maxParallelSubCalls pending shaped-append tasks
  the ordered commit lane holds (Promise.race drains one), so a slow spill
  backend backpressures the run instead of accumulating unbounded pending
  I/O and retained results. Tasks self-remove on settlement; run
  settlement still drains every task inside the open turn. New spill test
  drives three oversized reads against a hung backend at cap 1 and proves
  the third dispatch cannot start until a save drains.
- shapeDispatchLog's catch uses errorMessage() (total), so a thrown value
  with a throwing toString cannot escape the containment and lose the
  settle event.
- CodeDispatchLog.content documented as the RENDERED result projection
  (native tool/result vocabulary), not what the program received — the
  program gets the structured value; doc pair + type-equiv re-synced.
- New RECORDED tui-agent snapshot scenario code-mode-dispatch-spill: the
  real Loader-visible composition (worker runtime + spill-local + policy)
  drives an oversized bash sub-call end-to-end; replay proves the durable
  dispatch copy is bounded to preview + locator while the program value
  stays whole (the outer result carries just the line count).

Agent Note updated (both languages).

docs/core-data-structures/tools.md

@@ -238,8 +238,10 @@ Code Mode's bridge additionally exposes each settled sub-dispatch to the `tools/
  * One settled `run_code` sub-dispatch about to be logged, as seen by the
  * `tools/code-dispatch-log` waterfall: the parent execution (session owner,
  * outer call identity), the sub-call identity, and the outcome whose durable
- * copy a listener may reshape. The complete `content` is what the program
- * already received; only the `tool/code-dispatch` event's copy changes.
+ * copy a listener may reshape. `content` is the RENDERED result projection
+ * (what a native `tool/result` would carry) — the program itself received
+ * the structured `value` (or just the error message on failure); only the
+ * `tool/code-dispatch` event's copy changes.
  */
 interface CodeDispatchLog {
   /** The outer `run_code` execution. */