* Add end-to-end ProcessAsync test for transient-pause (required + non-required)

The P1b transient-pause fix (#434) was covered only compositionally: the
unit tests mock the phase to throw the transient directly, and
HalibutResumeReattachTests calls the strategy directly — neither runs the
real ExecuteSingleActionAsync per-action catch THROUGH the runner to the
pause outcome. The non-required path (no per-target catch) was the gap the
adversarial review flagged.

This drives the REAL pipeline: IDeploymentTaskExecutor.ProcessAsync over a
seeded deployment (KubernetesAgent target, so the real
HalibutMachineExecutionStrategy records the in-flight pointer), with only
the Halibut RPC transport faked (GetStatus throws a transient
HalibutClientException). It asserts, for BOTH required and non-required
steps: task Paused (not Failed), checkpoint preserved, and the in-flight
pointer preserved.

Red-green verified: with the ExecuteSingleActionAsync transient catch
neutered, the NON-required case fails (Paused → Failed + checkpoint
deleted) — the exact swallow bug — while the required case still passes
(the per-target catch covers it), confirming the test specifically guards
the non-required propagation the fix added.

* Tighten transient-pause E2E: typed pointer reader + permanent-failure contrast

Replace the brittle Contains("\"t\"") substring with the production typed
reader InFlightScriptMap.TryGet(json, DispatchSlot(...)) asserting the preserved
pointer holds the EXACT ScriptTicket the strategy dispatched (captured in the
fake) — pins slot identity + ticket value and survives a JsonPropertyName rename.

Add a permanent-failure contrast case: the same seeded path with a permanent
Halibut subtype (ServiceNotFoundHalibutClientException) must Fail terminally +
delete the checkpoint, so the Paused rows read as "Paused iff transient" and the
transient/permanent boundary is pinned end-to-end, not just in the predicate's
own unit test.