docs(6207): migrations 0088 and 0090-0094 state their rationale in terms of the data

Milestone/step labels, record ids, the rescoped-rule date and the 296-call
measurement go; each header states what the change protects. "rule 36"
citations become the DROP + ADD practice they named.

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

alembic/versions/0094_rule_usage_events.py

@@ -1,4 +1,4 @@
-"""add rule_usage_events — was a surfaced rule ever read? (milestone 333 step 1)
+"""add rule_usage_events — was a surfaced rule ever read?
 
 Revision ID: 0094
 Revises: 0093
@@ -9,18 +9,15 @@ table to arrive after `rule_embeddings` and `rule_versions` — each one added
 because the rule side kept inheriting machinery built for notes and getting
 the weaker version of it.
 
-WHAT IT MEASURES. The write-path standing-rule arm is the only retrieval
-surface in Scribe whose usefulness cannot be observed, and — not coincidentally
-— the only one that has never declined to fire. Over 30 days it took 296 calls,
-returned something on every one, and cleared its threshold 100% of the time,
-while every other surface declines most of the time (#3311). That is either a
-perfectly tuned surface or a bar it cannot fail to clear, and `retrieval_logs`
+WHAT IT MEASURES. A standing-rule arm that returns something on every call
+and clears its threshold every time is either a perfectly tuned surface or a
+bar it cannot fail to clear, and `retrieval_logs`
 cannot tell them apart: it records what the ranker scored, never whether the
 hint was any use.
 
 WHY NOT A rule_id COLUMN ON note_usage_events. The row shares no note-specific
 fields and the aggregate readout is the same shape, which is the strongest case
-for sharing that note #3163 admits. What decides against it is identity at
+for sharing there is. What decides against it is identity at
 RESTORE: `note_usage_events`'s importer maps `note_id` through `note_id_map`
 and drops what does not resolve. A rule id parked in that column would come
 back from a backup silently reattached to whatever note took that number —
@@ -34,8 +31,8 @@ and dies with it; telemetry outlives the row it describes. Deleting a rule must
 not erase the evidence that it was surfaced forty times and opened never, since
 that evidence is exactly the case for having deleted it.
 
-No CHECK on `event`, matching the note twin. Rule 36 governs adding a value to
-a column that is already gated; it does not require gating one that never was,
+No CHECK on `event`, matching the note twin. DROP + ADD governs adding a value
+to a column that is already gated; it does not require gating one that never was,
 and a two-member enum whose members are written by two functions in one module
 is not where that discipline earns its cost.