Forward instructor comments and edits into a running session #22

Outcome

An instructor's comment or body edit during a build reaches the session, and an outsider's edit stops the build, as in softfac.

Acceptance criteria

• Instructor comments and body edits on a building issue are sent into its thread with softfac's message wording and forward-wait steps.
• A body or title edit by someone who is not an instructor makes the run stuck with softfac's reason.
• softfac's runner test sections "forwarding: the messages", "forwarding: comments", "forwarding: a body edit", "forwarding: guards and failures" and "forwarding: waiting for the run a message starts" are ported and pass.

Depends on

• Handover: the fork's factory is ready to build this repo #21

Notes

This issue is for the fork's own factory, after the handover in #21. Leave it at factory:proposed until the fork's factory watches this repo.

Reference

• softfac, the Rust factory this ports, pinned at rawphp/softfac@bf273a1. Read it from a separate clone: git clone --filter=blob:none https://github.com/rawphp/softfac /tmp/softfac-ref && git -C /tmp/softfac-ref checkout bf273a1d93651992b4fc95b4dd6c111f8f3322cf. Its docs/lifecycle.md, docs/reference/ledger.md and docs/issues.md describe the behaviour; its tests pin it.
• Design: factory/docs/design.md in this repo.
• Upstream's AGENTS.md applies. Run only the tests and typechecks for the paths you touch (vp test run <path>, vp run --filter t3 typecheck), never the repo-wide checks.
• Edit no upstream file that is not listed in factory/SEAMS. A new seam needs a line in factory/SEAMS and a reason in the PR body.
• Port behaviour, not code: port the named test cases first (TypeScript, vitest / @effect/vitest), then make them pass. Exact comment and ledger wording is ported as is.