A pre-trigger hook returning decision:"hold" WITH mutations had them
discarded at parse (parse_output mapped "hold" to a data-less outcome),
so the approval-gate pattern (hold AND stamp validated context) was
impossible. HookOutcome::Hold now carries HookMutations via a shared
parse_mutations helper, and run_pre_trigger folds the holding hook's
argument rewrite into the effective arguments before parking. Those args
ride the call checkpoint added for #506 (fix/506-release-runs-original-args,
which this is based on), so the resolve(execute) release runs with the
gate's mutation.

Unquarantines C-E2E-505, now a regression gate.

Fixes #505

…ated arguments (#520)

* fix(harness): release held calls with hook-mutated arguments

A call held by a pre_trigger hook and released with
harness::function::resolve {action: "execute"} ran the target with the
model's ORIGINAL arguments recovered from the transcript — mutations from
hooks that ran before the holder were dropped, and the remaining chain
never resumed, breaking the harness.md § function::resolve promise that
the pre_trigger chain resumes after the holding hook.

- PreTriggerOutcome::Hold now carries the arguments as mutated up to the
  hold; the loop persists them on the call's checkpoint (held_arguments),
  so they survive the park durably. Post-trigger holds checkpoint the
  fully pre-mutated args for the same reason.
- The execute release path prefers the checkpointed arguments (transcript
  recovery remains the fallback for records written before the field
  existed), resumes the pre_trigger chain AFTER the holder — hooks up to
  and including it already ran, so re-running would double-apply
  mutations and re-hold — and handles a resumed Deny/Hold like the loop.
  The filesystem scope stamp is still re-applied after the resumed chain.
- A holder no longer bound at release runs no further hooks: the chain
  shape changed under the hold and the safe resume point is unknowable.

Fixes #506

* test(conformance): unquarantine C-E2E-506 — regression gate for #506

The fix on this branch makes the scenario pass; --scenario all (and the
per-PR CI job) now executes it. Verified locally: C-E2E-001, C-E2E-002,
C-E2E-506 all pass.

* fix(harness): pre-trigger hold keeps its own argument mutations (#519)

A pre-trigger hook returning decision:"hold" WITH mutations had them
discarded at parse (parse_output mapped "hold" to a data-less outcome),
so the approval-gate pattern (hold AND stamp validated context) was
impossible. HookOutcome::Hold now carries HookMutations via a shared
parse_mutations helper, and run_pre_trigger folds the holding hook's
argument rewrite into the effective arguments before parking. Those args
ride the call checkpoint added for #506 (fix/506-release-runs-original-args,
which this is based on), so the resolve(execute) release runs with the
gate's mutation.

Unquarantines C-E2E-505, now a regression gate.

Fixes #505

* test(integration): retry empty descendant PID reads