docs(6209): wide net, startup, stamps, slippage, miss route and parity tests

Eight more test files state the property they pin as a present-tense
fact. Incident narratives (a dated storage stall, a week of zero tuning
events, a two-project poisoned ledger, a twenty-site owner audit) become
the failure shape each test defends; one-install figures that name a rule
become a general worked example with the calibration numbers kept. The
family-grouping regression guard is renamed for what it checks.

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

tests/test_retrieval_miss_route.py

@@ -1,18 +1,13 @@
-"""A recognized retrieval miss has a route, and the route is ordered (#4133).
+"""A recognized retrieval miss has a route, and the route is ordered.
 
 WHY THIS EXISTS
 
-Milestone 416 built the tuning loop across steps 4 and 6 — `retrieval_surfaces`
-to read a dial, `tune_retrieval` to move one with its argument attached,
-`migrate_retrieval_floor` to carry it across a model change — and then measured,
-on 2026-09-17, that `retrieval_tuning_history` returned **zero events**. Not one
-call, ever.
-
-The cause was not a tool being wrong. The three tools appeared on NO instruction
-surface: not the skills, not the hooks, not the MCP `_INSTRUCTIONS`. They were
-classified in `server.py`'s read/write lists and named nowhere a session would
-read them. The operator's decision for #4102 — *"the model should be the thing
-handling it 9 times out of 10"* — could not begin to happen.
+The tuning loop is three tools — `retrieval_surfaces` to read a dial,
+`tune_retrieval` to move one with its argument attached,
+`migrate_retrieval_floor` to carry it across a model change — and the model is
+meant to be the one using them most of the time. A tool classified in
+`server.py`'s read/write lists and named on no instruction surface is never
+called: nothing a session reads tells it the tool exists.
 
 So this file guards a ROUTE, not a behaviour: that a session which notices a
 rule missed the moment it governed has somewhere written down to take it.
@@ -27,13 +22,12 @@ computed against, so a miss is evidence about that text first; a floor is one
 number governing every record on the surface and cannot tell a badly-worded
 trigger from a genuinely distant one.
 
-Measured on this install, which is why the order is asserted rather than
-suggested: rule 1 "`dev` is home" scored 0.6515 and ranked 5th for the moment it
-governed, behind three rules that RESTRAINED the same act. Every percentile said
-"lower the floor" — and at 0.60 the arm delivered those three restraints and
-still not rule 1. Rewriting the trigger to lead with the symptom put the same
-rule 1st at 0.7130. The dial-first path was available, statistically supported,
-and wrong.
+Which is why the order is asserted rather than suggested: a rule can score
+0.65 and rank fifth for the moment it governs, behind rules that RESTRAIN the
+same act. Every percentile says "lower the floor" — and at 0.60 the arm
+delivers those restraints and still not that rule, while rewriting its trigger
+to lead with the symptom puts it first at 0.71. The dial-first path can be
+available, statistically supported, and wrong.
 """
 from __future__ import annotations
 
@@ -50,8 +44,8 @@ TUNING_TOOLS = ("retrieval_telemetry", "update_rule", "retrieval_surfaces",
 
 
 def _skill() -> str:
-    # The route lives in missed-retrieval.md, a reference file of using-scribe
-    # (#4398); the skill is SKILL.md and its references read together.
+    # The route lives in missed-retrieval.md, a reference file of using-scribe;
+    # the skill is SKILL.md and its references read together.
     from tests.helpers import skill_text
     return skill_text("using-scribe")
 
@@ -142,17 +136,16 @@ def test_writing_a_new_record_asks_what_already_covers_the_moment():
 
 
 def test_the_route_stays_off_the_index():
-    """`_INSTRUCTIONS` is the only surface every MCP client gets (decision #4027).
+    """`_INSTRUCTIONS` is the only surface every MCP client gets.
 
-    It carried a one-line MISSED pointer to this route until #4389, which found
-    the index was being used as a rulebook: a missed rule is noticed mid-work,
-    not at session start, and the spec asks server instructions for the
+    It carries no pointer to this route, because the index is not a rulebook:
+    a missed rule is noticed mid-work, not at session start, and the spec asks server instructions for the
     workflow across tools, not stance. using-scribe states the route (the tests
     above pin it); the index keeps what_might_apply, the tool that opens it.
 
     Whitespace-flattened before matching: the block is hard-wrapped, so a
-    phrase straddles a line break the moment anything before it changes length
-    (#4103).
+    phrase straddles a line break the moment anything before it changes
+    length.
     """
     text = " ".join(_instructions().split()).lower()
     assert "what_might_apply" in text