feat(moments): mount the corpus by proposal - a pass and an open-after-moment signal, both stopping at the operator (milestone 458 step 7, #4925)

A rule written before moments existed is mounted on nothing. Step 7 records,
per (rule, moment), whether it belongs there and who said so:

- rule_moment_judgments (migration 0118, backup v23): suggested / confirmed /
  rejected, from a pass, the signal, or an edit. Moment "" is "no moment fits".
- The pass: rules_to_mount lists unjudged rules; propose_rule_moments records
  suggestions that mount nothing; rule_moment_proposals and
  judge_rule_moments put them to the operator. A confirm mounts, a reject is
  kept so the pair is never proposed again. Same service behind REST and a
  "Waiting on you" panel in Settings > Moments.
- Edits are judgments: set_rule_moments, the one mount write path, confirms
  what was added and rejects what was removed in the same transaction.
- The signal: scribe_moment.sh keeps a per-session acts ledger; when a rule
  is opened, scribe_record_opened.sh sends the last three minutes of it to
  /api/plugin/rule-opened. The acts resolve through the install's mappings;
  work.run and work.change are not evidence. Counted per distinct session
  with lesson_rules' evidence model, and once due the open returns one line
  asking the reader to offer the mount.
- scribe_session_end.sh removes the session's scribe-moment files.

Plugin 2026.10.05.2003.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scribe/services/lesson_rules.py

@@ -485,16 +485,18 @@ async def attach_rule_lessons(user_id: int, data: dict, rule_id: int) -> None:
 def situation_key(arm: str, text: str) -> str:
     """A fingerprint of one situation, so a repeat counts once.
 
-    `arm` is part of the key — "p" for a prompt, "w" for a file being written
-    — because the two name different kinds of situation and must not collide.
+    `arm` is part of the key — "p" for a prompt, "w" for a file being written,
+    "s" for a session (the rule↔moment signal, milestone 458 step 7) —
+    because each names a different kind of situation and must not collide.
     On the prompt arm the text is the prompt: lowercased, split into word
     tokens of _MIN_TOKEN or more, de-duplicated and sorted, so the same ask
     re-sent with different spacing, punctuation, case or word order is one
     situation. On the write arm the text is the PATH, not the code: every
     edit to one file is one situation, however much the code differs between
-    them. Empty when there is nothing to key on.
+    them. The session arm keys on the session id as given. Empty when there
+    is nothing to key on.
     """
-    if arm == "w":
+    if arm in ("w", "s"):
         basis = (text or "").strip()
     else:
         tokens = sorted({t for t in re.findall(r"[a-z0-9]+", (text or "").lower())