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/playsessions/service.go

@@ -1,6 +1,6 @@
-// Package playsessions implements the listening-session lifecycle: a session is a contiguous sequence of plays by a user with no
-// gap longer than the configured timeout (default 30 minutes) between
-// events.
+// Package playsessions implements the listening-session lifecycle: a session is
+// a contiguous sequence of plays by a user with no gap longer than the
+// configured timeout (default 30 minutes) between events.
 package playsessions
 
 import (
@@ -34,7 +34,8 @@ func FindOrCreate(
 		return pgtype.UUID{}, err
 	}
 	if err == nil {
-		// "Within window" includes the exact-boundary case: gap <= timeout extends.
+		// "Within window" includes the exact-boundary case: gap <= timeout
+		// extends.
 		gap := eventTime.Sub(prev.LastEventAt.Time)
 		if gap <= timeout {
 			if err := q.TouchPlaySessionLastEvent(ctx, dbq.TouchPlaySessionLastEventParams{