test(hooks): snapshot the CC + Codex hook matrix end-to-end

Load both hook bridges in the ACP example (dsh-hooks-claude → ./hooks.json,
dsh-hooks-codex → ./codex-hooks.json) so the full-transcript snapshot tier can
exercise each dialect against the real app. An absent config file is a silent
no-op, so a scenario carries only the file it needs and the other bridge
vanishes — verified byte-identical against every pre-existing snapshot.

Add a scenario per hook point × its headline Decision outcome, both dialects:
UserPromptSubmit block (authored, keyless) + context-fold, PreToolUse deny/ask,
PostToolUse block/context, Stop force-continue. The mid-turn scenarios are
recorded against the real API with the hook active, so the model's reaction to
a denied/blocked/force-continued turn is part of the replayed transcript.

SessionStart and SubagentStart are deliberately excluded (detached best-effort
inject races the log position — a recorded golden fails 10/10 on its own
replay), as is SubagentStop (observe-only, zero transcript footprint — a golden
could never be proven to fail). Both stay on the bridges' unit coverage. See
docs/rfc/implemented/testing/2026-07-04-hook-snapshot-matrix.md.

docs/rfc/README.md

@@ -155,6 +155,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
 | [Per-session snapshot replay for nested agents](implemented/testing/2026-06-22-subagent-snapshot-replay.md) | 2026-06-22 |
 | [Persist the seed boundary so fork-child replay routes correctly](implemented/testing/2026-06-22-fork-child-replay-seed-boundary.md) | 2026-06-22 |
 | [Record fork and mixed spawn+fork snapshot scenarios](implemented/testing/2026-06-22-fork-snapshot-scenarios.md) | 2026-06-22 |
+| [Hook snapshot matrix — end-to-end goldens for both bridges](implemented/testing/2026-07-04-hook-snapshot-matrix.md) | 2026-07-04 |
 
 ## Rejected