docs(6209): coverage, guidance-ownership, shape, warnings tests and shared fixtures

test_pattern_coverage, test_guidance_ownership, test_integration_shape_classify,
test_instruction_surfaces_agree, test_retrieval_warnings, helpers.py and
conftest.py state the property each test or fixture holds. The issue and
milestone numbers, consolidation dates and one-install measurements that
recorded how each was found are dropped; fixture dates and ids stay.

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

tests/test_instruction_surfaces_agree.py

@@ -1,29 +1,11 @@
 """What the instruction surfaces must say that one owner per topic cannot enforce.
 
-WHY THIS FILE IS SMALLER THAN IT WAS
-
-Until milestone 410 this file pinned REDUNDANCY: every session-start surface —
-the MCP `_INSTRUCTIONS`, the plugin's static context, the `using-scribe` skill —
-had to restate how a rule reaches a session, what an empty session means, the
-Systems reflex and the snippet-recording triggers. That was the design #2494
-chose after #2497 (two surfaces disagreeing about who loads the rules) and
-#2198 (every hook silently inert): say it everywhere, so no single failure
-loses it.
-
-Decision #4027 replaced that with ownership, and tests/test_guidance_ownership.py
-now enforces it: every topic stated in full by exactly one owner, with a
-one-line pointer in the server's index. The tests that required every surface
-to repeat itself were retired there, because they enforced the very duplication
-that drifted (#4022). What they protected is still protected:
-  - "state how to ask for a rule" / "say an empty session is not an empty
-    rulebook" → the rules topic: owned by using-scribe, indexed in
-    `_INSTRUCTIONS` with both phrases;
-  - the Systems reflex and the snippet-recording triggers → their topics'
-    markers, required on their owners;
-  - "never name the SessionStart push without stating the ask" (#2497's exact
-    shape) → retired outright. Since milestone 394 the push carries no rules,
-    so naming it can no longer imply rules were handled, and requiring every
-    surface that mentions it to restate the ask would force a copy.
+tests/test_guidance_ownership.py enforces who states each topic: every topic
+stated in full by exactly one owner, with a one-line pointer in the server's
+index. How to ask for a rule and what an empty session means are the rules
+topic, owned by using-scribe and indexed in `_INSTRUCTIONS`; the Systems
+reflex and the snippet-recording triggers are their topics' markers, required
+on their owners.
 
 WHAT STAYS HERE
 
@@ -46,7 +28,7 @@ def _all_surfaces() -> list[tuple[str, str]]:
     what the hook does is not the same act as telling an agent it need not pull.
     The boundary is "does a session read this", which is skills (loaded by
     description match, and each reference file a skill links is read on its
-    own, so it is its own surface — #4398), the hook-injected static context, and the MCP server's
+    own, so it is its own surface), the hook-injected static context, and the MCP server's
     own instructions.
     """
     found = [(str(p.relative_to(ROOT)), p.read_text())
@@ -68,10 +50,9 @@ def _instructions_text() -> str:
 
 
 # Claude Code injects only the first ~2,048 characters of an MCP server's
-# instructions and silently cuts the rest mid-word (#2562: observed live —
-# the previous 20k-char version delivered ~10% of itself, and none of the
-# Systems tagging guidance ever reached a session). The budget is set below
-# the cap, not at it: the field runs ~600–1,600 characters (spike #4389), and
+# instructions and silently cuts the rest mid-word, so guidance past the cap
+# never reaches a session. The budget is set below the cap, not at it: the
+# field runs ~600–1,600 characters, and
 # a block pressed against 2,048 is being used for depth that belongs in a
 # skill.
 INSTRUCTIONS_BUDGET = 1600
@@ -81,18 +62,17 @@ def test_instructions_fit_the_fold():
     text = _instructions_text()
     assert len(text) <= INSTRUCTIONS_BUDGET, (
         f"_INSTRUCTIONS is {len(text)} chars; Claude Code injects only ~2,048 "
-        f"and silently cuts the rest (#2562). This block is an INDEX — state "
-        f"the topic in full on its owner (a skill or the tool's docstring, "
-        f"decision #4027) and give it at most a line here; see the comment "
+        f"and silently cuts the rest. This block is an INDEX — state "
+        f"the topic in full on its owner (a skill or the tool's docstring) "
+        f"and give it at most a line here; see the comment "
         f"above _INSTRUCTIONS."
     )
 
 
 # ── force: a surface that says rules bind must say what does not ────────
 #
-# Added with the preference kind (milestone 399). Before it, "rules bind" was
-# the whole truth and every surface said so flatly. It is now half of one, and
-# the half that is missing is the dangerous half to omit: a session reading
+# With a preference kind beside rules, "rules bind" is half of the truth, and
+# the missing half is the dangerous half to omit: a session reading
 # only "rules bind" and then receiving a preference has been told, by the most
 # authoritative surface it has, to treat it as binding.
 #
@@ -107,7 +87,7 @@ def test_instructions_fit_the_fold():
 # PINNED ON THE CLAIM, NOT THE WORD "bind". A bare substring also matches
 # `bind_repo`, `list_repo_bindings` and the DNS-rebinding comment in
 # server.py — so it would one day fail a skill that mentions repo binding and
-# has nothing to do with force, which is rule 167's named failure: a guard
+# has nothing to do with force — a guard
 # raising a false alarm about the very thing it protects. These phrases are
 # the ones that actually assert bindingness to a reader.
 BINDING_CLAIMS = (
@@ -144,7 +124,7 @@ def test_a_surface_claiming_rules_bind_also_names_what_does_not():
 # 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
+# The currency half is the central claim: 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.
@@ -168,12 +148,12 @@ def test_the_index_names_all_three_strengths():
         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)."
+        f"using-scribe."
     )
 
 
 def test_the_strength_guard_can_fail():
-    """Rule 167. The guard has to be able to bite, and it bites on omission —
+    """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."
@@ -182,14 +162,13 @@ def test_the_strength_guard_can_fail():
     assert missing == ["that lessons inform"]
 
 
-# ── Reporting back (milestone 409 step 3) ──────────────────────────────
+# ── Reporting back ─────────────────────────────────────────────────────
 #
 # The reporting-back skill carries the shapes, but a skill only helps if it
 # fires. The reflex that sends a session to it is stated in using-scribe, and
 # the in-band cue on update_task (`placement`, `report_back`) is the half that
-# fires on its own in every client. The server's index carried a REPORT line
-# until #4389: reporting is a mid-work stance, not a session-start practice. The
-# static context was a second plugin-side copy until milestone 410.
+# fires on its own in every client. The server's index carries no REPORT line:
+# reporting is a mid-work stance, not a session-start practice.
 
 REPORT_REFLEX = "report back in a shape the operator can read"
 REPORT_SURFACES = (
@@ -211,8 +190,8 @@ def test_the_reporting_reflex_is_stated_in_using_scribe():
 
 
 def test_the_reporting_reflex_takes_placement_from_the_record():
-    """The failure milestone 409 began from: a placement reconstructed from
-    memory reads exactly like a real one when it is wrong."""
+    """A placement reconstructed from memory reads exactly like a real one
+    when it is wrong."""
     for path in REPORT_SURFACES:
         text = " ".join(path.read_text().split())
         assert "`placement`" in text, f"{path.relative_to(ROOT)} no longer points at the placement block"