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_retrieval_surfaces.py

@@ -1,19 +1,11 @@
-"""The surface registry, and the identity the whole tuning story rests on (#4102).
+"""The surface registry, and the identity the whole tuning story rests on.
 
 WHY THIS EXISTS
 
-Six arms used to own their own numbers: a settings key, a default, and a limit
-that was usually a module constant nobody could change. That survived while the
-values were shipped constants. It stops surviving once the operator's decision
-is that the numbers MOVE:
-
-    "the floor should be chosen and adjusted by the model using it… the user
-    should be able to touch it but the model should be the thing handling it 9
-    times out of 10."
-
-A tuning surface cannot be model-consistent across arms that each spell their
-configuration differently, so the arms now read `{floor, budget}` from one
-registry.
+The retrieval floors MOVE: the model using an arm chooses and adjusts them, and
+a person can too. A tuning surface cannot be model-consistent across arms that
+each own a settings key, a default and a limit spelled their own way, so the
+arms read `{floor, budget}` from one registry.
 
 WHAT THIS PINS
 
@@ -24,9 +16,8 @@ WHAT THIS PINS
      different file. Renaming one without the other produces a surface that can
      be tuned and cannot be measured, or measured and not tuned, and both fail
      silently.
-  2. **Keys are unique.** Two surfaces sharing a settings key is how the
-     completion-report arm (since retired) spent its first release moving
-     whenever the prompt arm was tuned (#3860) — one dial wearing two labels.
+  2. **Keys are unique.** Two surfaces sharing a settings key move together
+     whenever either is tuned — one dial wearing two labels.
   3. **An unknown surface is refused.** Settings keys are free-form strings in
      a generic table, so a typo'd name would write a key nothing reads: a
      change that appears to succeed, reports a new value, and alters nothing.
@@ -63,7 +54,7 @@ def test_every_surface_name_is_a_real_telemetry_source():
     to justify a change describes a different arm from the one the change hits.
     """
     blob = "\n".join(_service_source(n) for n in SERVICES)
-    # The rule arms record through the one pipeline (milestone 456), where
+    # The rule arms record through the one pipeline, where
     # `source` is the spec's own field — so for them the spec IS the string
     # `record_retrieval` receives, and the join key is checked against it.
     from scribe.services.retrieval_pipeline import NOTE_ARMS, RULE_ARMS
@@ -81,7 +72,7 @@ def test_every_surface_name_is_a_real_telemetry_source():
 
 
 def test_no_two_surfaces_share_a_settings_key():
-    """One dial, one label. #3860 is what the other way costs."""
+    """One dial, one label."""
     floors = [s.floor_key for s in rs.SURFACES.values()]
     budgets = [s.budget_key for s in rs.SURFACES.values()]
     assert len(set(floors)) == len(floors), f"duplicate floor key in {floors}"
@@ -189,6 +180,6 @@ async def test_the_write_path_config_carries_every_arm_it_drives():
                 "tool_rule_threshold", "tool_rule_top_k",
                 # Not a surface, and that is why it is spelled out here: it
                 # has no floor/budget pair to derive from, so nothing else in
-                # this file would notice it going missing (#4214).
+                # this file would notice it going missing.
                 "checkpoint_threshold"):
         assert key in cfg, f"{key} missing — its arm will silently no-op"