samples mode: call-workflow replay drops the workflow name

[dsyme]

Summary

In samples mode, the dynamically generated call-workflow MCP tool now registers and replays, but the emitted canonical call_workflow message omits its workflow identity. The apply job rejects it with Workflow name is empty.

Follow-up to the call-workflow portion of #54811.

Evidence

Workflow sample:

samples:
  - workflow_name: "test-copilot-call-worker"
    inputs:
      sentinel: "${{ github.event.inputs.sentinel }}"

At github/gh-aw commit eaca36f, the replay server registers test_copilot_call_worker with metadata workflow: test-copilot-call-worker. apply_samples calls it with the sentinel and reports success. The apply stage then finds one call_workflow message but fails:

Workflow name is empty, skipping
Message 1 (call_workflow) failed: Workflow name is empty

The dynamic handler needs to materialize its _call_workflow_name metadata into the canonical field consumed by the apply handler, while preserving the sample inputs.

Parent: https://github.com/githubnext/gh-aw-test/actions/runs/32615153966
Child: https://github.com/githubnext/gh-aw-test/actions/runs/32616131682

[dsyme]

This overlaps with #54811 but is a follow-up rather than an exact duplicate. #54811 reported that the dynamic call_workflow tool was not registered (Tool not found). At eaca36f7a97c, registration and sample replay now succeed, but the replayed message loses the configured workflow identity and the apply stage fails with Workflow name is empty. Keeping this issue focused on that post-registration serialization defect.

[dsyme]

Reopening because the same post-registration defect reproduces on gh-aw main at commit 818e3a3 with --use-samples. Replay emits and ingestion validates {"inputs":{"sentinel":"..."},"workflow_name":"test-copilot-call-worker","type":"call_workflow"}, but the apply job still reports Workflow name is empty. Parent: https://github.com/githubnext/gh-aw-test/actions/runs/32926231185. Child: https://github.com/githubnext/gh-aw-test/actions/runs/32927799291 (apply failure at 2026-08-26T03:49:48Z).

[dsyme]

call-workflow still reproduces on gh-aw main bde2c79aa0d6 with --use-samples (AI not called). Parent: https://github.com/githubnext/gh-aw-test/actions/runs/33586188587 Child: https://github.com/githubnext/gh-aw-test/actions/runs/33587922577

Sample replay succeeds at 2026-09-02T03:42:06Z for test_copilot_call_worker, then safe_outputs fails at 03:42:39Z with Workflow name is empty.