feat(gcp-cloud-run): support plan protocol v2

[jrusso1020]

Summary

• add explicit, opt-in Plan protocol v2 support to the GCP Cloud Run adapter
• publish a manifest-last, content-addressed GCS artifact graph and verify every downloaded artifact
• materialize only chunk-scoped dependencies; download audio only for assembly
• keep Plan v1 as the default and fail closed on mixed or malformed protocol locators
• add SDK/workflow propagation, v2 sample events, and local contract coverage
• add an owner-isolated real-GCP v1/v2 parity smoke path with fail-closed cleanup

Stack

• based on feat(aws-lambda): support plan protocol v2 #2789 (AWS Lambda Plan v2)
• feat(aws-lambda): support plan protocol v2 #2789 is based on feat(producer): add content-addressed plan v2 #2788 (producer Plan v2)
• feat(producer): add content-addressed plan v2 #2788 is based on feat(producer): version distributed plan protocol #2777 (Plan protocol v1 boundary)

Safety

• no automatic protocol fallback after fan-out
• required GCP APIs are read-only preconditions; the smoke test never enables shared services
• generated repositories fail closed if already present
• image package/tag, Terraform state, service accounts, Cloud Run service, workflow, render bucket, and Cloud Build staging bucket are invocation-scoped
• Cloud Build upload is bounded to 526 files / 6,462,103 bytes
• cleanup deletes and absence-verifies only preflighted owner-scoped resources
• GCP retains only its Cloud Build execution and Cloud Logging/audit history

Validation

• 80 GCP adapter/workflow/smoke-safety tests
• GCP package typecheck and build
• oxlint and oxfmt
• Terraform fmt and validate
• shell syntax and tracked-artifact checks
• Fallow change audit: no introduced issues
• independent blocker review approved the default owner-scoped live test

Live gate

The PR is draft only because the configured jrusso-devbox gcloud credential
currently requires interactive reauthentication. After login refresh, run:

./examples/gcp-cloud-run/scripts/smoke.sh \
  --project jrusso-devbox \
  --region us-east2 \
  --protocols v1,v2 \
  --chunk-sizes 15 \
  --owner plan-v2-parity-20260725

Attach exact decoded video/audio/metadata parity and independent cleanup
evidence before marking ready.

[jrusso1020]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(gcp-cloud-run): support plan protocol v2 #2790 👈 (View in Graphite)
• feat(aws-lambda): support plan protocol v2 #2789
• feat(producer): add content-addressed plan v2 #2788
• feat(producer): version distributed plan protocol #2777
• main

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