feat(instructions): a rule proposal has five answers, and three of them route (#3733, #3896)

Step 6 of both milestone 385 (lessons) and 399 (preferences). #3896 asked for
the fourth and fifth answers in one pass, because two people each adding one
branch to a three-way distinction produce a list that does not read as a set.

create_rule now opens by asking what kind of thing is being held, with one
question that sorts it — what happens if someone doesn't do this? Something
breaks, a boundary is crossed: a rule. It gets done a way the operator didn't
want: a preference. They lose time rediscovering it: a lesson. The closing
question grew the two matching answers, and they are named as first-class
outcomes rather than places a proposal lands when it fails. An observation
that turns out to be a lesson has been routed, not dropped.

Stated as a practice, not a prohibition (rule 165). #3557's first cut opened
"NOT YOURS TO CALL UNPROMPTED" and cost the noticing; the wanted behaviour
here is still more proposals, and what changes is only which door they go
through.

create_note says the same from its side, so routing does not depend on having
opened create_rule first — and its existing rule test ("a mistake, not merely
uninformed") turned out to name the lesson exactly. create_lesson names the
fifth kind so the set is complete from every door. create_project_rule's
citation of the loop names five answers, since it cites rather than repeats.

The force axis has one owner (decision #4027): using-scribe states all three
strengths, the sorting question, that updating a preference mid-work is the
normal case, and that preferences shape how work is done and never what gets
recorded. _INSTRUCTIONS carries the pointer — "Rules bind; preferences guide
and you keep them current; lessons inform." It had 14 characters of headroom,
so the clause is paid for by trimming atmosphere from three other lines; 1998
of 2000 now.

Guards: the proposal-loop test learns the preference branch, the lesson
branch and the force question, on both rule surfaces; guidance-ownership gains
the force-axis topic (shared with the docstrings, for the moment a proposal is
actually written) and the preference-scope topic; a new guard pins that the
index names all three strengths and who keeps the middle one current, with its
can-fail case being the omission that actually happens — a kind added to the
product while the index still describes the corpus that came before it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_instruction_surfaces_agree.py

@@ -131,6 +131,53 @@ def test_a_surface_claiming_rules_bind_also_names_what_does_not():
     )
 
 
+# ── the index names every strength, and who keeps the middle one current ──
+#
+# Milestones 385 and 399 both end here, and for the same reason. The index is
+# the one guidance surface EVERY MCP client receives — a client that reads no
+# Agent Skills still gets it — so a strength the index omits does not exist for
+# that session. Before the lesson kind, "rules bind; preferences guide" was the
+# whole corpus; a session that meets a third line shape with no name for it
+# falls back on the nearest one it has, which is the binding one.
+#
+# The currency half is the claim #3896 was written around: a preference is the
+# one record a session updates ITSELF, without asking. Stated only in the
+# skill, it reaches a session that loaded the skill — which is exactly the
+# session least likely to need telling. In the index it reaches everyone.
+#
+# Words, not wording: each entry is a family, and a rewrite satisfies it by
+# saying the thing in any of these ways.
+INDEX_STRENGTHS = {
+    "that rules bind": ("rules bind",),
+    "that preferences guide": ("preferences guide",),
+    "that lessons inform": ("lessons inform", "lessons are", "a lesson informs"),
+    "that a preference is kept current": ("current",),
+}
+
+
+def test_the_index_names_all_three_strengths():
+    text = " ".join(_instructions_text().split()).lower()
+    missing = [claim for claim, family in INDEX_STRENGTHS.items()
+               if not any(t in text for t in family)]
+    assert not missing, (
+        f"_INSTRUCTIONS no longer says {missing}. It is the only guidance every "
+        f"client receives, and a record kind it does not name is one the session "
+        f"has to guess the force of — which it does by reaching for the kind it "
+        f"does know. Keep it to a clause; the full statement lives on "
+        f"using-scribe (decision #4027)."
+    )
+
+
+def test_the_strength_guard_can_fail():
+    """Rule 167. The guard has to be able to bite, and it bites on omission —
+    the failure that actually happens, when a kind is added to the product and
+    the index is left describing the corpus that came before it."""
+    text = "rules bind; preferences guide and you keep them current."
+    missing = [claim for claim, family in INDEX_STRENGTHS.items()
+               if not any(t in text for t in family)]
+    assert missing == ["that lessons inform"]
+
+
 # ── Reporting back (milestone 409 step 3) ──────────────────────────────
 #
 # The reporting-back skill carries the shapes, but a skill only helps if it