[patch] Assign release manifest owners - #46

Outcome

Make the existing platform release schema's ownership and signing roles machine-checkable without changing the v1 manifest format.

Changes

• add an exact leaf-field owner map bound to the v1 schema identity
• resolve every application family to one specialist owner
• name candidate producer, promoted-manifest signer, promotion approver, signature verifier, application evidence approver, and recovery evidence approver
• make the validator derive schema leaf paths and reject missing, extra, duplicate, or unaccountable owners
• document that promotion still requires a keyless OIDC signer and verification receipt

Evidence

• GNUPGHOME=$(mktemp -d) go test ./ci/github/...
• direct valid-manifest validator invocation with the schema and owner map
• git diff --check

Release status

This defines and validates ownership. It does not claim that a promoted manifest has been signed; candidates remain candidates until the OIDC signer and verification receipt exist.