chore(auth): prepare production Wolfi publication grant

.github/chainguard/README.md

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+# Production export-wolfi trust
+
+Publication writes only wolfi-dev/os; the export identity has no public-write grant.
+
+These policies are part of [OS-2867](https://linear.app/chainguard/issue/OS-2867).
+Follow the [production runbook](https://github.com/chainguard-dev/mono/blob/main/env/enforce.dev/iac/400-export-wolfi/README.md).
+
+Merge after staging memory acceptance and confirmed paused production
+infrastructure deployment. These policies bind dedicated production service
+accounts by their numeric `uniqueId`. Reconfirm the subjects against the stage's
+`octosts_policies` output and obtain review before merge. If an account is
+recreated, update its exact subject and repeat the policy checks and review.
+
+The three runtime-policy PRs can merge in parallel once their exact subjects are
+reviewed. Keep both new schedules paused while installing grants. Complete the
+single-writer handover and signed-history proof before merging activation. Runtime
+accounts have no git-export access; mono's existing build policy handles direct ko.

.github/chainguard/export-wolfi-publish.sts.yaml

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+# Production OS-2867: bind the dedicated account by its numeric uniqueId.
+# Re-review this subject if the service account is recreated.
+# Google service account: export-wolfi-publish@prod-enforce-fabc.iam.gserviceaccount.com
+issuer: https://accounts.google.com
+subject: "111686246305885758377"
+repositories:
+  - os
+permissions:
+  contents: write