build(tools): Overhaul RFD justfile workflow for multi-cycle reviews

[JeanMertz]

The rfd-review, and rfd-triage commands have been reworked to
support iterative review cycles without losing conversation context. A
new rfd-apply command is introduced to apply triage verdicts back to
the RFD file.

Two private helpers centralise repeated logic that was previously
copy-pasted across commands. _resolve-conversation TITLE looks up an
active conversation by title and prompts the user to continue,
archive-and-restart, or quit, emitting a tagged token the caller
dispatches on. _bear-note TAG resolves a Bear note by tag and prompts
when none is found, emitting FOUND/EDIT/CONTINUE/QUIT. Both pr-review
and pr-triage are updated to use _resolve-conversation in place of
their own inline lookup-and-prompt blocks.

rfd-review now titles its conversation rfd-review:<id>, supports
resuming that conversation across cycles, and — in continuation mode —
automatically attaches the latest user/assistant turn from the sibling
rfd-triage:<id> conversation so the reviewer can engage with the
triager's response from the prior round. Bear notes tagged
rfd/<id>/review are attached when found.

rfd-triage drops the positional MODE and CONVO arguments. It now
discovers the sibling rfd-review:<id> conversation automatically
(failing fast if none exists), titles its own conversation
rfd-triage:<id>, and supports continuation via
_resolve-conversation. Bear notes tagged rfd/<id>/triage are
attached when found.

rfd-apply is a new command that resumes the rfd-triage:<id>
conversation with the dev persona, re-attaches the current RFD file, and
instructs the model to apply only the triaged verdicts. Bear notes
tagged rfd/<id>/apply are attached when found.

The rfd-reviewer persona is updated to handle continuation rounds: it
now knows to engage with the jp:// triage attachment, acknowledge
resolved concerns, and re-raise unresolved ones rather than redoing
critique already applied.