feat(rules): rules before tools — a PreToolUse arm keyed on the action (#3476)

The only just-in-time rule surface was registered on `Write|Edit` and queried
with `code or path`, so a rule could be retrieved at the moment of a code
write and nowhere else. Every rule about which tool to reach for — don't curl
the forge, don't stand up a stack, don't run the suite locally, don't branch —
was unreachable exactly when it mattered, and residency in the always-on
preload was the only surface it had. That is the pressure that grew the
resident set to 31 against #3089's ceiling of ~23; it was never a judgment
anybody made.

A reflex generates no query, so an instruction to check the rules cannot catch
one. A mechanical trigger can: the tool call IS the query, and a reflex has to
become a tool call before it can do anything.

`build_tool_rule_hint` is deliberately tool-agnostic — a name and a string —
so widening the matcher later is a hooks.json edit with no server change. The
hook starts on Bash, which is where the action reflexes live.

The two pre-tool arms share ONE session ledger of already-named rules
(`<state>/<sid>.rules.ids`). Two ledgers would mean a rule named by one arm
gets re-offered by the other, and the hint that fires most often is exactly
the one that must not repeat itself. A test asserts both scripts build the
same path, and another checks the shell hook and the Python route agree on
every query-arg name (rule 33) — a rename there fails silently, looking like
a surface that never finds anything rather than a broken one.

Deliberately silent on outage, unlike the prior-art hook: a write is
occasional, a Bash call is not, and an outage line before every command is
what gets a channel muted.

`tier="conditional"` matches the write arm and is the transition point — an
always-on rule is already resident, so re-tier one and it starts arriving here
instead of in every session's preamble. `pre_tool_rule` joins RANKED_SOURCES:
this arm chose what it showed, so a pull can settle whether the choice landed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011cPyzNnegXHr5iRMzzy5KJ

src/scribe/routes/plugin.py

@@ -101,6 +101,46 @@ async def autoinject_retrieve():
     return jsonify(result)
 
 
+@plugin_bp.get("/tool-rules")
+@login_required
+async def pre_tool_rules():
+    """Standing rules for the plugin's PreToolUse hook on ACTIONS (#3476).
+
+    Answers "does a recorded rule speak to the command about to be run?" — the
+    sibling of /prior-art, which can only answer that question about a code
+    write. Rules about which tool to reach for (don't curl the forge, don't
+    stand up a stack, don't run the suite locally) had no retrieval surface at
+    all before this, which is why they all had to live in the resident preload.
+
+    Titles + trigger only, never the statement: the hint says a rule may apply
+    and hands over `get_rule(id)`. One rule at most (RULEHINT_LIMIT), and empty
+    most of the time.
+
+    Query:
+        tool (str)              — the tool about to run, e.g. `Bash`. Used in
+                                  the hint's wording, not in the search: a
+                                  rule is about the action, not the harness.
+        command (str)           — the command about to run; the semantic query.
+                                  Absent or blank → empty, no search.
+        repo (optional)         — working repo remote, resolved to the bound
+                                  project exactly as /retrieve and /prior-art.
+        exclude_rule_ids (opt)  — comma-separated rule ids already surfaced
+                                  this session. SHARED with /prior-art's
+                                  ledger on purpose: one session keeps one
+                                  list, so a rule named by either arm is not
+                                  re-offered by the other.
+    """
+    tool = (request.args.get("tool") or "tool").strip()
+    command = request.args.get("command") or ""
+    project_id, _repo, _unbound = await _project_scope()
+    exclude_rule_ids = _int_list(request.args.get("exclude_rule_ids"))
+    result = await plugin_ctx_svc.build_tool_rule_hint(
+        g.user.id, tool, command,
+        project_id=project_id, exclude_rule_ids=exclude_rule_ids,
+    )
+    return jsonify(result)
+
+
 @plugin_bp.get("/prior-art")
 @login_required
 async def write_path_prior_art():