docs: api comments say what the endpoints do, not how they came to be (#6277)

Rewrites the internal/api comment blocks to rule 32: task, milestone and
rule ids gone, the stories behind them restated as the constraint they
left, stale references corrected (the stream secret is wired from config,
the timezone handler already refreshes the scheduler, the Android app is
the native client, the design docs cited are not in the repo). Also
rewraps comment lines over 80 columns left by the earlier batches.

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

internal/api/admin_recommendation_trends.go

@@ -1,6 +1,6 @@
-// Admin recommendation-trends endpoint (#1251): weekly per-surface
-// outcome series with tuning-audit markers — the verify half of the
-// tune→verify loop the tuning lab (#1250) opens. Aggregated across
+// Admin recommendation-trends endpoint: weekly per-surface outcome
+// series with tuning-audit markers — the verify half of the tune→verify
+// loop the tuning card opens. Aggregated across
 // all users because the knobs are global; rows carry rates only.
 package api