Add replayable feedback transition export

[bytemain]

Summary

• derive a minimized feedback transition view from the existing append-only audit log
• expose app-scoped opaque cursor paging for status, assignee, and comment-visibility transitions
• report independent coverage boundaries for each transition type
• publish the endpoint through OpenAPI and the agent action manifest

Security and data boundaries

• returns only ticket id, transition type, transition values, and occurrence time
• does not project actors, comment ids or bodies, reporter identifiers, audit payloads, contacts, device metadata, webhook data, or secrets
• binds cursors to one app and preserves the existing app-viewer authorization boundary
• makes the audit source immutable while the app exists so derived sequences cannot drift; app purge remains supported

Validation

• Worker typecheck
• Worker tests: 332 passed
• focused transition/material tests: 13 passed
• migration validator, query-plan assertions, cursor isolation, nullable assignee, no-op, purge, and forbidden-payload tests
• git diff --check