## Summary

Small replay omission found while auditing the completed #655 extraction
after #686 merged. All eight planned slices are already on `main`; this
is a narrowly scoped correctness follow-up, not another feature tranche.

A legacy `spawnAgent` record can establish a coordinator's identity and
parent without an agent path. Later replay may supply that coordinator's
path and newly recorded nested child activity. Previously
`announceHistory` returned immediately for the known coordinator,
discarding the available path. The nested activity then could not
resolve its immediate parent, so valid descendant history was omitted
with a gap advisory.

Fill a known child's **missing** normalized path from recorded activity
before descending into its history. Do not replace an already observed
path with older history. Identities, established parent links, titles,
runtime ownership, capabilities, AIR behavior, and v1/v2 negotiation
remain unchanged.

**2 files, +39/-1 lines. No snapshot changes.**

## Regression evidence

- Four v1/v2 warm/cold replay cases failed on current `main` before the
fix: a live or restored pathless coordinator prevented newly recovered
descendant text from replaying.
- Those four cases now replay the text under the correct immediate
parent without a false gap.
- Two additional v1/v2 cases preserve an already observed parent path
when an older spawn record disagrees.

## Validation

- `npm run typecheck`
- `npm test`: **2,070 passed**, 39 skipped
- `npm run build`
- `npm run test:integration`: **15 passed** against real Codex 0.164.0
with a local mock Responses API
- `npm run bundle:all`: all six targets compiled
- `git diff --check`

The full live-model E2E suite and an additional live-model smoke test
were not run for this fix. Cross-platform bundles were compiled, not
executed on each target OS.

## Audit context

The remaining old #655 diff largely reflects replaced implementations,
differently organized tests/snapshots, and intervening trunk work such
as native model reporting. In particular its older queue-completion
helper and model implementation must not replace the corrected trunk
versions. The combined PR should not be merged wholesale.

Checked current specification revision
`c0897908cb2305e89203218c348d69ab4acf9d61`. This fix retains the [RFD's
truthful identity, parentage, and parent-before-child replay
ordering](https://github.com/agentclientprotocol/agent-client-protocol/blob/c0897908cb2305e89203218c348d69ab4acf9d61/docs/rfds/subagents.mdx#L724-L755);
it adds no wire fields or mutation authority.