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>

plugin/hooks/scribe_moment.sh

@@ -0,0 +1,118 @@
+#!/usr/bin/env bash
+# Scribe — PreToolUse moment arm: rules MOUNTED on a moment arrive when the
+# moment happens (milestone 458 step 4).
+#
+# The other PreToolUse arms search: they turn the act into a query and hope a
+# rule's words resemble it. A mount needs no resemblance. The operator said
+# "this rule applies when work is delivered", the install maps `git push` onto
+# work.deliver, and so `git push` brings the rule — whatever the command's
+# words happen to be. The server resolves the call to its moments and looks up
+# what is mounted there; this hook only carries the event and the answer.
+#
+# REGISTERED ON EVERY TOOL, KEPT OFF THE WIRE FOR MOST OF THEM. Which calls can
+# reach a mounted rule depends on this install's mappings and mounts, so the
+# matcher cannot say. Instead the hook keeps the server's answer to "which
+# tools can?" (`/moment-tools`) on disk for a few minutes, and a call to any
+# other tool costs one file read. An install that has mounted nothing gets an
+# empty list and never sends a moment request at all.
+#
+# SCRIBE'S OWN TOOLS ARE SKIPPED. Closing a task or recording a lesson reaches
+# its moment through the tool's own response (`moment_rules`), which works for
+# a client without this plugin too; delivering it here as well would say it
+# twice.
+#
+# SILENT ON OUTAGE, like scribe_tool_rules.sh and for its reason: this fires
+# before many calls, and an outage line before each is noise. A failed list
+# fetch is cached as an empty list, so a down instance costs one timeout per
+# window rather than one per call.
+#
+# Env:
+#   SCRIBE_URL / SCRIBE_TOKEN override for the settings.json dogfooding path.
+
+command -v curl >/dev/null 2>&1 || exit 0
+
+# shellcheck source=plugin/hooks/scribe_defs.sh
+. "$(dirname "${BASH_SOURCE[0]}")/scribe_defs.sh"
+
+event=$(cat 2>/dev/null || true)
+event_flat=$(printf '%s' "$event" | scribe_json_flat)
+tool_name=$(scribe_json_pick "$event_flat" '.tool_name')
+session_id=$(scribe_json_pick "$event_flat" '.session_id')
+event_cwd=$(scribe_json_pick "$event_flat" '.cwd')
+
+[ -n "$tool_name" ] && [ -n "$session_id" ] || exit 0
+
+case "$tool_name" in
+  mcp__*scribe*__*) exit 0 ;;
+esac
+
+scribe_config || exit 0
+
+# The tool's KEY, as the server writes mappings: no MCP server prefix, lowercase.
+tool_key=${tool_name##*__}
+tool_key=$(printf '%s' "$tool_key" | tr '[:upper:]' '[:lower:]')
+
+state_dir="${TMPDIR:-/tmp}/scribe-priorart"
+mkdir -p "$state_dir" 2>/dev/null || true
+safe_sid=$(printf '%s' "$session_id" | tr -c 'A-Za-z0-9._-' '_')
+
+# ── Which tools can reach a mounted rule: cached, first line a timestamp ──
+#
+# Five minutes. A mount or a mapping made in this session reaches the hook
+# within that window; the MCP door delivers Scribe's own moments at once.
+# Not a `.ids` file, so a compaction does not sweep it: it describes the
+# install, not what this context holds.
+tools_file="$state_dir/${safe_sid}.moment.tools"
+now=$(date +%s 2>/dev/null) || now=0
+stamp=""
+[ -f "$tools_file" ] && stamp=$(head -n 1 "$tools_file" 2>/dev/null)
+case "$stamp" in ''|*[!0-9]*) stamp=0 ;; esac
+if [ "$now" -eq 0 ] || [ $((now - stamp)) -gt 300 ]; then
+  listed=$(curl -fsS --max-time 3 \
+    -H "Authorization: Bearer ${token}" \
+    "${url%/}/api/plugin/moment-tools" 2>/dev/null) || listed=""
+  {
+    printf '%s\n' "$now"
+    scribe_json_list "$(printf '%s' "$listed" | scribe_json_flat)" '.tools'
+  } > "$tools_file" 2>/dev/null || true
+fi
+tail -n +2 "$tools_file" 2>/dev/null | grep -Fqx -- "$tool_key" || exit 0
+
+# ── The moment request ────────────────────────────────────────────────────
+
+repo_q=""
+lookup_dir=${event_cwd:-${CLAUDE_PROJECT_DIR:-$PWD}}
+scope=$(scribe_scope_query "$lookup_dir")
+[ -n "$scope" ] && repo_q="&${scope}"
+
+# The shared session ledger, as scribe_tool_rules.sh reads and writes it: a
+# rule this session was already shown is cited, not quoted again.
+rulefile="$state_dir/${safe_sid}.rules.ids"
+ledger_q=""
+rule_seen=$(scribe_rules_live "$rulefile")
+[ -n "$rule_seen" ] && ledger_q="&exclude_rule_ids=${rule_seen}"
+ledger_q="${ledger_q}$(scribe_held_query "$state_dir/${safe_sid}.opened.ids")"
+
+# The event whole, since which field a mapping matches is the mapping's
+# business. A write of a very large file is reduced to its name: the moments a
+# write reaches never depend on its content.
+if [ "${#event}" -gt 65536 ]; then
+  esc=$(printf '%s' "$tool_name" | scribe_json_escape) || exit 0
+  event="{\"tool_name\":\"${esc}\",\"tool_input\":{}}"
+fi
+
+query="${repo_q}${ledger_q}"
+query=${query#&}
+body=$(printf '%s' "$event" | curl -fsS --max-time 3 \
+  -H "Authorization: Bearer ${token}" \
+  -H "Content-Type: application/json" \
+  --data-binary @- \
+  "${url%/}/api/plugin/moment${query:+?$query}" 2>/dev/null) || exit 0
+
+body_flat=$(printf '%s' "$body" | scribe_json_flat)
+scribe_json_list "$body_flat" '.rule_ids' | scribe_rules_append "$rulefile"
+
+context=$(scribe_json_pick "$body_flat" '.context')
+[ -n "$context" ] || exit 0
+scribe_json_out PreToolUse "$context"
+exit 0