docs(jobs): correct two migration citations and the import dedup contract

The retention-purge comments still cite migration 0277 for indexes that landed
in 0276 — the renumbering moved the directories and left the prose behind. The
schema is trustworthy because its comments are, so a wrong number is not
cosmetic.

The import worker's `already_recorded` reason claimed the skip covers a dose
recorded on any other intake surface. It does not: `source` is part of the
live-row unique, so a hand-logged dose and an imported one at the same slot are
different keys and both are written. Say what the mechanism actually does, and
say plainly that cross-surface dedup is not there.

src/lib/jobs/audit-log-cleanup.ts

@@ -37,7 +37,7 @@ export function getAuditLogRetentionDays(): number {
  * on every removed row. Past the 60-second `statement_timeout` that aborts and
  * rolls back, and the next night repeats it against the same rows — a
  * retention window that can never close on an instance that has accumulated
- * enough of them. Migration 0277 adds the `created_at` index; the batching
+ * enough of them. Migration 0276 adds the `created_at` index; the batching
  * keeps any single statement bounded regardless.
  */
 export async function cleanupOldAuditLogs(

src/lib/jobs/measurement-tombstone-cleanup.ts

@@ -38,7 +38,7 @@ function tombstoneCutoff(now: Date): Date {
  * the transaction rolled back, and the next night ran the identical statement
  * against the same rows. `measurements` is the densest table in the schema and
  * a bulk source delete can tombstone a six-figure row count in one action, so
- * this is the one most likely to have been stuck. Migration 0277 adds the
+ * this is the one most likely to have been stuck. Migration 0276 adds the
  * partial index the predicate needs.
  */
 export async function cleanupExpiredMeasurementTombstones(

src/lib/jobs/medication-intake-import.ts

@@ -58,8 +58,13 @@ export interface MedicationImportPayload {
  *
  * `duplicate_in_file` — two rows of the same submission resolve to the same
  * medication and slot, so only one can be written.
- * `already_recorded` — the dose is already on the ledger for that slot, from an
- * earlier import or from any other intake surface.
+ * `already_recorded` — the dose is already on the ledger for that slot from an
+ * earlier import. `source` is part of the live-row unique
+ * `(user_id, medication_id, scheduled_for, source)`, so this does NOT cover a
+ * dose the person logged by hand at the same slot on another surface: that row
+ * and the imported one are distinct keys and both are written. Cross-surface
+ * dedup is a slot-window question, not a unique-key one, and it does not exist
+ * yet — do not read this reason as though it did.
  *
  * Those two used to be one `skippedDuplicates` number, which is how a file whose
  * every row collapsed onto one key could report "27 duplicates skipped" about 27