Refine ticket

Revisits an existing open ticket at `docs/tickets/open/{slug}/index.md` and improves it in place – assesses it against the ticket template, verifies its code references against the current codebase, then interviews the user one question at a time and edits as answers land. Use when the user says "refine the X ticket", "revisit X", "flesh out the X ticket", "update the spec for X", or runs `/refine-ticket`. Edits an open ticket in place and makes the small related edits its answers settle – the initiative's `## Tickets` list, a spike's missing `findings.md`, an `initiative:` retag – without a second question; never moves, closes, or deletes docs, never touches source code,…