chore(auth): prepare production Wolfi publication grant

[joedborg]

Why

The production publisher needs public repository write access without granting that access to the exporter.

How

Add an organization-hosted policy for the dedicated production publisher, restricted to repositories: [os] and contents: write. Keeping it outside mirrored history avoids policy commits diverging the publication branch.

Merge in step 2 after staging acceptance, fresh CI, and review. The paused foundation deployment is confirmed and the verified production numeric subjects are now populated. Keep the new schedules paused through policy installation and handover.

Proof

The production foundation deployment applied successfully at 2026-09-29 13:01:33 UTC (27 added, 0 changed, 0 destroyed). It deployed 20b01d2cc011307f62d7e389dc31355ea4ad1c8e, a verified descendant of merged foundation f605768657b04638e6d2a552ec3ff4cdd09c8514.

Direct GCP IAM reads and the run's tf-output-env-enforce.dev-iac-400-export-wolfi artifact agree:

Account	Numeric subject
export-wolfi@prod-enforce-fabc.iam.gserviceaccount.com	100496071258544612791
export-wolfi-publish@prod-enforce-fabc.iam.gserviceaccount.com	111686246305885758377

All four prepared policy YAMLs structurally equal the deployment's octosts_policies outputs. Live read-only checks confirmed both jobs Ready at observed generation 1, saved DRY_RUN=true, empty bootstrap, separate runtime accounts, expected repositories/branches/horizon/signer, 2 CPU/8 GiB, and zero task retries. Both Scheduler jobs are PAUSED (hourly export; daily 14:00 UTC publication).

Both deployed image signatures were independently verified with cosign against exact identity https://github.com/chainguard-dev/mono/.github/workflows/.terraform.yaml@refs/heads/main and issuer https://token.actions.githubusercontent.com. Export digest: sha256:6027800bd11f80eeaecc6df67b4c7d158df1da87657524f29c87853e7f867027; publication digest: sha256:3d99353bb87f53adaf822cdc24789f6b5ccb2252e6e44a1c41b3bee2c999a279.

Both job-failure alert policies are enabled with troubleshooting documentation and the expected enabled destinations: #eng-os-prod-alerts, shared Pub/Sub alerts, and OS Pub/Sub alerts_os. This is a configuration check, not notification-delivery proof.

Pinned yam formatting, strict OctoSTS v0.8.0 schema/compile/scope/permission checks, and diff checks pass. For each policy, synthetic claims with the configured production subject are allowed; the opposite production identity, staging/dev identities, fixture subjects, empty subject, wrong issuer and wrong audience are rejected. These are offline authorization checks; production runtime token exchange and Git writes remain part of the later handover proof. Two independent reviews found no remaining findings.

The source-policy PR additionally passed all applicable stereo pre-commit hooks individually (yam, misspell, YAML, Markdown, large-file/case/conflict/private-key/todo checks). The all-hooks launcher initially failed installing the unrelated wolfictl package linter after a Go proxy stream error; that linter does not apply to these files. The temporary checker passed gofmt, go mod tidy, go test (no test files), and golangci-lint. No proof files were committed.

Merge order

0. Staging gate: mono#62720 deployed; real-publication peak-memory evidence accepted.
1. Foundation: chainguard-dev/mono#62783. Merged and deployed paused/dry-run on September 29; successful deployment evidence.
2. Runtime policies, parallel after step 1: chainguard-dev/stereo#356262; chainguard-dev/.github#324; wolfi-dev/.github#133. Production numeric subjects are populated and verified against IAM and deployment outputs. Require fresh CI and review before merging.
3. Stop Actions: chainguard-dev/stereo#356263. During the owned handover window, disable schedules/manual dispatch and drain queued/active runs before new writers may run.
4. Legacy retirement after step 3: chainguard-dev/wolfi-staging#25 and chainguard-dev/git-export#160. Remove the destination grant in wolfi-staging only, before selecting the bootstrap SHA. Publication carries the same deletion into public; do not open a divergent public-policy removal commit. Keep mono's build-time policy.
5. Operator handover proof: freeze/review destination history, review the exact bootstrap SHA, prove real export parity/signing and exact-commit publication with schedules still paused. Recheck every export advancement and publish only the final verified tip.
6. Activation LAST: chainguard-dev/mono#62787. Merge only after the handover evidence is accepted, then have an authorized operator deploy it and verify natural scheduled execution.

Merging is not deployment. This PR set does not authorize or perform production releases, local production plans/applies, or runtime writes. Full procedure: production runbook. Tracking: OS-2867.