docs(notes): the surfaces say WHEN a note earns a check, and a guard keeps them saying it (#3168, milestone 317 step 5)

The step that decides whether steps 1-4 were worth building. `verify_with` is
a free-text field on the highest-volume record kind in the product; described
only as "how to verify this note" it gets filled in on every note within a
week, and at that point the sweep returns the whole corpus and means nothing.
The signal is not "has a check" — it is "has a check AND almost nothing else
does".

Rule 119 puts this in the app's own instruction surfaces, never in a Scribe
rule. So:

- the using-scribe skill gains the reflex, next to "state updates in place;
  chronicles don't" — its other half, since supersession only fires once
  somebody has read a note and disagreed, which is the case where it was
  already believed;
- update_note's docstring now states the DEFAULT rather than only deferring
  to create_note for the test. Found by the new guard on its first run;
- plugin 0.1.48.

THE _INSTRUCTIONS BUDGET, decided rather than skipped. The payload is ~1980 of
the client's ~2048-char cap, so everything in it competes for the last ~68
characters. The operator declined a line for this milestone: the map's own
closing sentence says each tool's description carries the full contract, and
the sweep is a curation act rather than a session-start reflex like
enter_project or list_always_on_rules. That reasoning is now a comment beside
the constant, with the accepted cost named — an agent that never opens
create_note's docstring never learns the field exists — so the question is not
re-litigated blind.

The guard pins STRUCTURE, never wording, for the disambiguator's reason (a
test that punishes rewriting is a test that gets deleted): each write surface
must still draw the norm-vs-constraint distinction, say the empty case is
normal, and name where NOT to reach for it — plus that the skill carries the
one-question form, because the docstrings only reach a caller who already
opened the tool.

`_doc` moves to tests/helpers as `tool_doc`; it had been written twice.

tests/test_create_tools_disambiguate.py

@@ -29,6 +29,7 @@ parameters, with the "is this even the right tool" paragraph quietly gone.
 import re
 
 import pytest
+from tests.helpers import tool_doc as _doc
 
 # The create surfaces and where they live. `start_planning` is here because
 # it is a create in everything but name — it is how a plan comes into being.
@@ -50,21 +51,6 @@ _ALTERNATIVES = [
 ]
 
 
-def _doc(module: str, name: str) -> str:
-    """The docstring with its whitespace flattened.
-
-    Flattened because a docstring is hard-wrapped: "design system" spans a
-    line break in at least one of these, and matching the raw text would
-    report it absent. The first draft of this check did exactly that, and
-    caught it on itself.
-    """
-    import importlib
-
-    fn = getattr(importlib.import_module(module), name)
-    assert fn.__doc__, f"{name} has no docstring at all"
-    return re.sub(r"\s+", " ", fn.__doc__)
-
-
 @pytest.mark.parametrize(("module", "name"), _SURFACES)
 def test_a_create_surface_names_at_least_two_alternatives(module, name):
     """Reaching for the wrong tool must still put the right one in view."""