Wire Apple KMS release signing

evolution/proposals/BEP-0009-release-infrastructure-and-store-upload-pipeline.md

@@ -47,7 +47,7 @@ The same change also makes the forge itself the release authority: release tags
   - `//bazel/apple:release_macos_stamp`
   These targets wrap the existing Xcode project and give the workflow one stable entrypoint that shares the same Bazel/Nix cache setup while Burrow decides whether deeper `rules_apple` targets are worth the migration.
 - Use Namespace cache setup before Bazel/Nix work. Prefer the Namespace Bazel remote cache when `nsc` is authenticated and fall back to a local disk/repository cache when remote setup is unavailable.
-- Produce unsigned Apple validation artifacts when signing is absent, but require signing for an App Store requested iOS release. Uploadable artifacts are produced only when signing assets are installed and provisioning profiles can be synced from App Store Connect credentials.
+- Produce unsigned Apple validation artifacts when signing is absent, but require signing for an App Store requested iOS release and for a Sparkle tester release. Uploadable artifacts are produced only after provisioning profiles can be synced from App Store Connect credentials and the relevant Apple certificate is proven to match the selected Google KMS key.
 - Resolve release credentials through age/agenix before signed Apple lanes run. Forgejo secrets should carry only the runner age identity fallback and the Authentik WIF client secret until OpenBao can mint the runner token directly. App Store Connect keys and signing certificates live as sealed files under `secrets/`.
 - Persist the forge runner SSH key as `/var/lib/forgejo-runner-agent/age_keystore` and export `BURROW_RUNNER_AGE_IDENTITY_PATH` so jobs can resolve agenix identities without embedding long-lived material in every workflow.
 - Add `Scripts/forgejo-dispatch.sh` and `Scripts/forgejo-dispatch-via-host.sh`:
@@ -58,7 +58,7 @@ The same change also makes the forge itself the release authority: release tags
 - Keep the canonical Forgejo repo as an ordinary source repository, not a mirror. The host config disables new mirror creation and removes mirror/push-mirror rows for the canonical Burrow repository at activation time.
 - Add `.forgejo/workflows/infra-opentofu.yml` and `Scripts/grafana-tofu.sh` for Grafana API-managed folders and dashboards. NixOS owns the Grafana service, SSO, reverse proxy, datasources, Prometheus, OpenTelemetry collector, Jaeger, secrets, and boot-time configuration; OpenTofu owns API-created dashboard objects.
 - Sync provisioning profiles from App Store Connect in CI using the decrypted API key:
-  - iOS App Store profiles for `com.hackclub.burrow` and `com.hackclub.burrow.network`.
+  - iOS App Store profiles for `net.burrow.app` and `net.burrow.app.network`.
   - macOS Developer ID profiles for the same bundle identifiers.
   Provisioning profile `.age` files are not part of the normal release path.
 - Add a non-exportable Google KMS RSA-2048/SHA-256 key named
@@ -85,6 +85,16 @@ The same change also makes the forge itself the release authority: release tags
   sync must verify App Store profiles reference that certificate. Stale profiles
   with the same name may be deleted and recreated so CI does not silently sign
   against an older distribution identity.
+- Apple release signing uses a staged KMS flow because Google publishes the
+  Cloud KMS PKCS#11 library for Linux release runners, not macOS runners:
+  - macOS Namespace builders compile unsigned iOS device and macOS app bundles
+    with the existing Xcode project.
+  - Linux release runners download those staged artifacts, authenticate to
+    Google through Authentik WIF, verify the Apple `.cer` public key matches the
+    intended Google KMS key version, embed the synced provisioning profiles, and
+    sign the app/extension bundles with the patched `rcodesign` PKCS#11 path.
+  - The signed iOS IPA is uploaded to App Store Connect, and the signed macOS
+    ZIP is used as the Sparkle tester artifact.
 - Add a non-exportable Google KMS key named `sparkle-ed25519` for Sparkle
   appcast signatures. It uses `EC_SIGN_ED25519` with software protection level
   because Google KMS rejects Ed25519 for HSM protection. macOS builds embed
@@ -97,7 +107,7 @@ The same change also makes the forge itself the release authority: release tags
 - Treat Sparkle as a macOS public-channel upload lane:
   - Generate staged appcast content from the signed macOS artifact when present.
   - Publish `sparkle/<channel>/`, `sparkle/appcast.xml`, and `sparkle/default/` pointers from `publish-store-uploads`.
-  - Full Sparkle client integration remains a follow-up because the current Apple app does not embed Sparkle.
+  - The macOS app embeds Sparkle and consumes the `https://releases.burrow.net/sparkle/appcast.xml` feed.
 - Add `infra/releases` as the OpenTofu boundary for the GCS release and package repository backup buckets. Garage is the required S3-compatible primary distribution target after host bootstrap. `infra/identity` remains the boundary for Google KMS signing keys, the Authentik WIF pool/provider, and the runner service account.
 
 ## Security and Operational Considerations
@@ -110,8 +120,13 @@ The same change also makes the forge itself the release authority: release tags
 - rclone is not part of the release path. Multi-cloud failover should be added through provider-specific or S3-compatible wrappers with explicit credentials and evidence.
 - Required upload credentials are checked explicitly after `./.forgejo/actions/decrypt-release-secrets` materializes them from age:
   - `secrets/apple/appstore-connect.env.age`: `ASC_API_KEY_ID`, `ASC_API_ISSUER_ID`, and base64-encoded `.p8` key material.
-  - `secrets/apple/distribution-signing.env.age`: base64-encoded distribution `.p12` plus its password.
-  - `secrets/apple/sparkle.env.age`: base64-encoded Sparkle EdDSA private key.
+  - KMS-backed Apple signing must not use `.p12` private-key material. The
+    legacy `secrets/apple/distribution-signing.env.age` path remains accepted
+    only for emergency keychain signing and should not be used for the normal
+    tester release lane.
+  - Sparkle appcasts are signed with Google KMS by default; the legacy
+    `secrets/apple/sparkle.env.age` path remains accepted only for emergency
+    local EdDSA signing.
   - future Microsoft Partner Center credentials
 - The temporary CI keychain password is always the distribution certificate password; there is no separate keychain-password release secret.
 - KMS-backed Apple certificates do not satisfy the existing Xcode/keychain