docs(6209): twelve more test files say which behaviour they pin

shape ledger, MCP projects/search/rulebooks tools, backup, chunking,
plugin context, derived mirror, rule band, shape form gate, plugin
version mint and note usage tests drop issue, milestone and rule numbers,
dates and one-install figures from docstrings, comments and messages.
Three shape-form-gate test names that told the discovery story now name
the property: a registry module's helpers are not service functions, the
divergence gate silences only a family contradiction, and callable helpers
beside a callable canon still prompt. The rulebook tool-count comment that
logged each milestone's additions is replaced by the reason it is a count.

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

tests/test_derived_mirror_generic_door.py

@@ -12,19 +12,19 @@ The failure is silent and the wrong way round, because every read PREFERS the
 mirror — deliberately, since parsing markdown to answer what an index can
 answer is how a hot path rots.
 
-  - A SNIPPET went on reporting its old repo/path/symbol to the location
+  - A SNIPPET goes on reporting its old repo/path/symbol to the location
     reverse lookup and to prior-art recall while displaying its new body: a
     record surfaced with full authority and wrong, which the drift-check
-    docstring calls worse than having no record at all (#3128).
+    docstring calls worse than having no record at all.
 
   - A LESSON is worse. Its mirror holds the TRIGGER, and the trigger is the
     entire retrieval story — a stale one keeps the lesson firing for the
     situation it used to name while it displays the one it now names.
 
-#3128's fix was correct and did not generalise: it tested one constant, so
-milestone 385's lesson arrived with the same design and none of the protection.
-The registry tests below assert the PROPERTY — every kind with a derived mirror
-is registered — so a third kind fails here rather than shipping quiet (#3734).
+A fix that tests one constant does not generalise: the next kind arrives with
+the same design and none of the protection. The registry tests below assert
+the PROPERTY — every kind with a derived mirror is registered — so a third
+kind fails here rather than shipping quiet.
 """
 import inspect
 
@@ -114,30 +114,30 @@ async def test_a_title_change_reaches_the_mirror_too():
 
 
 def test_every_kind_with_a_derived_mirror_is_registered():
-    """The load-bearing one. Before #3734 this was a single `if` naming
-    snippets, and the kind added next was simply not covered."""
+    """The load-bearing one. A single `if` naming one kind leaves the next
+    kind uncovered."""
     from scribe.services.lessons import LESSON_NOTE_TYPE
     from scribe.services.notes import _mirror_recomposers
     from scribe.services.snippets import SNIPPET_NOTE_TYPE
 
     table = _mirror_recomposers()
-    assert SNIPPET_NOTE_TYPE in table, "the #3128 fix was lost"
+    assert SNIPPET_NOTE_TYPE in table, "snippets lost their mirror recomposer"
     assert LESSON_NOTE_TYPE in table, (
         "a lesson's `data` holds its trigger and `lesson_trigger` prefers it, "
         "so a body edit through the generic door would leave the lesson being "
-        "retrieved for a situation it no longer names (#3734)"
+        "retrieved for a situation it no longer names"
     )
 
 
 def test_the_dispatch_is_a_lookup_not_a_named_kind():
-    """Asserted on structure (rule 167). A lookup extends in one line in one
+    """Asserted on structure. A lookup extends in one line in one
     place; naming a kind inline is the shape that left lessons uncovered."""
     from scribe.services import notes as notes_module
 
     src = inspect.getsource(notes_module.update_note)
     assert "_mirror_recomposers()" in src
     assert "SNIPPET_NOTE_TYPE" not in src, (
-        "update_note names one kind again — that is the shape #3734 replaced"
+        "update_note names one kind inline — the dispatch must be a lookup"
     )
 
 
@@ -184,7 +184,7 @@ async def test_a_body_write_moves_a_lessons_trigger_with_it():
 async def test_a_subject_containing_an_em_dash_still_splits():
     """Why `untrigger_title` is given the trigger instead of splitting on the
     separator: a subject may legitimately contain one. The title here is an
-    UN-MIGRATED one, still carrying its trigger (milestone 427), because that
+    UN-MIGRATED one, still carrying its trigger, because that
     is the row the inverse still has to read correctly."""
     from scribe.services.embeddings import trigger_title
     from scribe.services.lessons import TRIGGER_KEY
@@ -259,8 +259,8 @@ async def test_a_lesson_title_change_reaches_the_mirror():
     ],
 )
 def test_untrigger_title_inverts_trigger_title(subject, trigger):
-    """#3207's shape: the join had three copies before it was consolidated, so
-    its inverse lives beside it rather than in whichever caller wanted it."""
+    """The join's inverse lives beside it rather than in whichever caller
+    wanted it."""
     from scribe.services.embeddings import trigger_title, untrigger_title
 
     title = trigger_title(subject, trigger)
@@ -289,12 +289,12 @@ def test_the_trigger_separator_is_spelled_in_exactly_one_place():
     ]
     assert not offenders, (
         f"the trigger separator is spelled inline in {offenders} — use "
-        f"TRIGGER_SEP, trigger_title or untrigger_title (#3207)"
+        f"TRIGGER_SEP, trigger_title or untrigger_title"
     )
 
 
 def test_the_mirror_guards_can_fail():
-    """Rule 167: shown turning red once."""
+    """Shown turning red once."""
     from scribe.services.lessons import TRIGGER_KEY, recompose_data
 
     bare = fake_lesson(title="just a title", body="no composed lines", data=None)