feat(moments): mounted rules arrive when their moment happens, through every door (milestone 458 step 4a, #4922)

A rule mounted on a moment now reaches the session when an act reaches
that moment, with no semantic match involved:

- run_moment_arm on the pipeline: a lookup, not a ranked search. Each
  line names the moment and the act that reached it ("at work.deliver,
  reached by `git push`"), so a misfire is visible where it lands and
  can be unmapped in-session. A repeat is cited, not quoted; fresh
  rules are recorded surfaced under source moment_rule with the moment
  in detail. No retrieval_logs row, as for the other lookups, so no
  latency is persisted for this arm.
- rule_scope: a rule's home clause, moved out of semantic_search_rules
  so the moment lookup scopes by the same one.
- rulebooks.rules_on_moments / mounted_moments.
- The plugin door: a catch-all PreToolUse hook (scribe_moment.sh). It
  keeps /moment-tools' answer on disk for five minutes, so a call to a
  tool that cannot reach a mounted rule sends nothing, and an install
  that has mounted nothing sends one request per window. It shares the
  rules ledger with the other arms and fails open silently.
- The MCP door: Scribe's own tools named by the shipped mappings carry
  moment_rules in their response, so a client without the plugin gets
  them too. The hook skips those tools. A guard pins the attach on
  every one.

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

scripts/check_plugin.py

@@ -341,6 +341,14 @@ SMOKE_EVENTS: dict[str, str] = {
         {"session_id": "smoke", "cwd": ".", "tool_name": "Bash",
          "tool_input": {"command": "curl -s https://example.invalid/api/v1/runs"}}
     ),
+    # The moment arm (milestone 458). A command the shipped mappings send to
+    # work.deliver, so a configured run reaches the moment-tools fetch and the
+    # moment request; with no instance both fail and it must stay SILENT,
+    # since it fires before every call that can reach a mounted rule.
+    "scribe_moment.sh": json.dumps(
+        {"session_id": "smoke", "cwd": ".", "tool_name": "Bash",
+         "tool_input": {"command": "git push origin dev"}}
+    ),
     "scribe_sync_processes.sh": json.dumps({"source": "startup"}),
     "scribe_session_context.sh": json.dumps({"source": "startup"}),
     # The after-write hook (#2901) diffs the working tree; on CI's clean