Generate GitHub Release update manifest

[cbusillo]

Objective

Generate a machine-readable update manifest from the canonical GitHub Release so internal dogfood builds can discover newer versions without relying on npm or Homebrew publishing.

Current Status

State: Waiting
Next action: Finish the release-path simplification in #126, then add manifest generation to the active Release workflow.
Blocked by: #126 release workflow decision.
Last verified: 2026-05-24 after deciding GitHub Releases should be the update source, not public package distribution.

Scope

• In: Release manifest schema, per-platform asset URLs, SHA256 hashes, version, commit, published timestamp, channel metadata, and workflow upload/publish behavior.
• Out: npm publishing, Homebrew publishing, public distribution branding, automatic binary replacement, or multiple update channels before stable is working.

Acceptance Criteria

• Release workflow emits an update manifest for the current GitHub Release.
• Manifest includes version, commit, published timestamp, channel, platform asset URL, and SHA256 for each supported target.
• Manifest is attached to the GitHub Release or otherwise retrievable from the release source of truth.
• Manifest generation fails the release before publication if required asset/hash data is missing.
• Docs state that GitHub Releases are the update feed for internal dogfooding.
• ./build-fast.sh passes for any repo/code changes.

Relationships

Depends on #126.
Follow-up for #85 internal fork/product direction.
Predecessor for a future CLI update-check/self-update implementation.

Notes

This issue exists because auto updates need an update source, not public package distribution. npm and Homebrew should remain deferred unless we separately decide we need package-manager installs.

[cbusillo]

Completed via PR #132 and release metadata PR #133.

What landed:

• scripts/release/generate-update-manifest.sh generates update-manifest.json from GitHub Release assets.
• The active Release workflow attaches the manifest before publishing the GitHub Release.
• Manifest includes schema version, version, stable channel, commit, published timestamp, platform asset URLs, SHA256 hashes, and sizes.
• Manifest generation fails if any expected platform archive is missing.
• docs/update-manifest.md, docs index, and .github/github.json now document/link the manifest contract.

Validation:

• Local fake-asset manifest generation passed.
• Local missing-asset failure path passed.
• ./build-fast.sh passed.
• PR feat: generate release update manifest #132 Blob size policy passed and merged.
• Release run 26370095181 passed and opened the v0.6.101 metadata branch.
• PR chore(release): prepare v0.6.101 #133 merged the metadata.
• Release run 26370810307 passed 8/8 jobs.
• GitHub Release v0.6.101 now includes update-manifest.json.
• Downloaded manifest verified with jq for schema/version/channel/platform coverage.