align(4909b): every write with a path gets its rule check, whether or not prior art matched

The write-path rule arm ran only past the notes guard: a write whose code
matched no snippet, issue or lesson returned before any rule was searched.
It now runs before that guard, on `code or path`, and a write that matched
nothing but a rule still returns the rule lines.

Operator ruling (2026-10-05): yes. A rule about the file being written does
not depend on a snippet resembling it.

Cost: one more rule search per write that matched no prior art, with its
own embedding (the query is `code or path`, not the notes arm's concept
query, so the per-request memo does not cover it). Plus the preference slot
from (c) on those writes.

Expected telemetry shift, to be read on its own once this reaches main:
write_path_rule calls rise toward write_path's count (14 days to 2026-10-22:
write_path_rule 4,634 against write_path 3,786 — the notes arm skips trivial
payloads, the rule arm does not, so the rule arm will now exceed it). Its
zero-result share rises too, since the newly covered writes are the ones
that matched nothing in the notes corpus.

Tests: the gate test is inverted (a write with no prior art still gets its
rule check); the design-only write now runs the rule arm on its path; two
notes-arm tests read the write_path row instead of any row, since the rule
arm writes its own.

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

tests/test_write_path_design_arm.py

@@ -181,12 +181,13 @@ async def test_a_ui_write_with_no_prior_art_still_hears_the_design_system():
 
 
 @pytest.mark.asyncio
-async def test_a_design_only_write_does_not_switch_the_rule_arm_on():
-    """The rule arm runs only where there is prior art. A design line that
-    joined that gate would start a semantic rule search on every UI write —
-    a new population of calls under a floor tuned without them."""
-    _, rules = await _hint(_quiet())
-    rules.assert_not_called()
+async def test_a_write_with_only_a_design_line_still_gets_its_rule_check():
+    """Every write with a path gets the rule check, prior art or not. With
+    nothing ranked, the design line still arrives on its own."""
+    out, rules = await _hint(_quiet())
+    rules.assert_awaited()
+    assert rules.await_args_list[0].args[1] == "frontend/src/B.vue"
+    assert out["context"].startswith("> Design system binds `frontend/src/B.vue`")
 
 
 @pytest.mark.asyncio