docs(6209): lesson links, design roles, version readout and endpoint, timestamp filters, settings defaults, opened ledger, surfaces

Eight more test files state their properties without issue, milestone and
rule numbers or dated regressions. The version tests describe what folding
the channel into the version breaks instead of the date it did; the surface
registry and settings-defaults tests state that floors move rather than
quoting the decision that made them move.

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

tests/test_rule_opened_ledger.py

@@ -1,17 +1,16 @@
-"""Named is not read: the ledger's third state (#4100).
+"""Named is not read: the ledger's third state.
 
 WHY THIS EXISTS
 
-Milestone 386 made a repeat REFERENCED rather than withheld, and the line it
-chose says "You saw it earlier this session". That claim was never checked.
-The arms emit a TEASER — title, trigger, `get_rule(N)` — so a session can be
+A repeat is REFERENCED rather than withheld, and a line that says "You saw it
+earlier this session" claims something nobody checked. The arms emit a TEASER — title, trigger, `get_rule(N)` — so a session can be
 shown a rule twenty times and never read a word of it, and a compaction
-summarises the teaser away leaving nothing at all. The server was asserting
-something about the reader's context it had no way to know.
+summarises the teaser away leaving nothing at all. The server would be
+asserting something about the reader's context it has no way to know.
 
 `.opened.ids` is the observable half, written by a PostToolUse hook from the
-`get_rule` call itself. That is why this is not the self-report 386 rejected:
-the objection was to ASKING a model about its own context, and a tool call is
+`get_rule` call itself. That is why this is not a self-report: the objection
+is to ASKING a model about its own context, and a tool call is
 an event the harness reports whether anyone asks or not.
 
 WHAT THIS PINS
@@ -82,8 +81,8 @@ def test_the_three_states_produce_three_different_lines():
 
 
 def test_held_outranks_seen_regardless_of_kind():
-    """`kind` moves the head and the ledger moves the tail; #3497's history is
-    the two being reasoned about together and one of them being forgotten."""
+    """`kind` moves the head and the ledger moves the tail; reasoning about
+    the two together is how one of them gets forgotten."""
     for kind in ("rule", "preference"):
         line = _rule_hint_line(_rule(kind=kind), where="here", seen=True, held=True)
         assert "opened it earlier" in line
@@ -139,7 +138,7 @@ def test_an_event_with_nothing_usable_records_nothing_and_still_exits_zero(event
 # that would be worst to get wrong — is asserted against the running hook in
 # tests/test_session_ledger_clear.py, so there is one home for it.
 #
-# Since #4217 the recorder writes TWO files and only this one is cleared.
+# The recorder writes TWO files and only this one is cleared.
 # `.opened.ids` says "this context holds rule 156", which a compaction makes
 # false, and three hooks read it to decide whether to stay quiet. Its twin
 # `.opened.keep.ids` says "rule 156 was opened", which a compaction does not