Add release/package operation evidence for SourceOS product surfaces

[mdheller]

Purpose

Make SourceOS-Linux/homebrew-tap the SourceOS packaging/distribution surface for product artifacts while preserving evidence, checksums, rollback notes, and Operation Plane release records.

Scope

Package and release support for:

• SourceOS-Linux/TurtleTerm
• SourceOS-Linux/BearBrowser
• SourceOS-Linux/sourceos-devtools
• SourceOS-Linux/agent-machine
• SourceOS-Linux/sourceos-syncd

Required operation types

• release.package.prepare
• release.formula.update
• release.checksum.verify
• release.evidence.attach
• release.rollback.record

Required artifacts/evidence

• package formula
• checksum record
• release note
• rollback note
• build/test evidence link
• source commit reference
• artifact provenance record

Integration targets

• SocioProphet/delivery-excellence#8
• SourceOS-Linux/sourceos-devtools#19
• SourceOS-Linux/TurtleTerm tracked through SocioProphet/workspace-inventory#4
• SourceOS-Linux/BearBrowser#20
• SourceOS-Linux/agent-machine#18
• SourceOS-Linux/sourceos-syncd#3
• SocioProphet/prophet-core-ledger#1

Acceptance criteria

• Formula/package updates include evidence links, checksums, and rollback notes.
• Release packaging is represented as a WorkspaceOperation or release evidence record.
• Packaging repo does not become runtime or policy authority.
• README or docs explain how package release evidence maps back to source repos.

Hard rule

Packaging is distribution, not runtime governance. Releases must carry evidence; they must not bypass contracts, tests, or policy gates.

[mdheller]

@copilot please implement this as a bounded release/package evidence slice.

Scope:

• Add docs and examples that map package/formula updates to Operation Plane release records.
• Cover release.package.prepare, release.formula.update, release.checksum.verify, release.evidence.attach, and release.rollback.record.
• Add evidence examples for package formula, checksum record, release note, rollback note, build/test evidence link, source commit reference, and artifact provenance.
• Cover package surfaces for TurtleTerm, BearBrowser, sourceos-devtools, agent-machine, and sourceos-syncd.

Use current seams:

• SocioProphet/prophet-core-contracts#1 release/package fixture.
• SocioProphet/prophet-core-ledger#1 evidence records.
• SourceOS-Linux/sourceos-devtools#19 validation/redaction tooling.
• SocioProphet/delivery-excellence#8 delivery governance.

Validation:

• Add fixture validation if repo conventions support it.
• Do not implement runtime policy, build system replacement, or product runtime logic here.

PR evidence required:

• Summary of files changed.
• Validation commands run and output.
• Explanation of how release evidence links back to source repos and rollback notes.