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_tuning.go

@@ -1,8 +1,8 @@
-// Admin recommendation-tuning endpoints (#1250): the defaults-
-// discovery lab. GET returns current values + shipped defaults for
+// Admin recommendation-tuning endpoints: the lab for finding good
+// defaults. GET returns current values + shipped defaults for
 // every scope; PATCH applies a partial update to one scope; reset
 // restores a scope to shipped defaults. Every change writes an audit
-// row (consumed by the metrics trend view, #1251).
+// row (consumed by the metrics trend view).
 package api
 
 import (
@@ -67,7 +67,7 @@ func tasteRespFrom(t recsettings.TasteTuning) tasteTuningResp {
 	}
 }
 
-// discoverTuningResp is the Discover scope on the wire (#2377).
+// discoverTuningResp is the Discover scope on the wire.
 type discoverTuningResp struct {
 	TagOverlapWeight float64 `json:"tag_overlap_weight"`
 	SnoozeDays       float64 `json:"snooze_days"`
@@ -113,7 +113,8 @@ func (h *handlers) tuningSnapshot() tuningSnapshot {
 	return out
 }
 
-// handleGetRecommendationTuning implements GET /api/admin/recommendation-tuning.
+// handleGetRecommendationTuning implements GET
+// /api/admin/recommendation-tuning.
 func (h *handlers) handleGetRecommendationTuning(w http.ResponseWriter, _ *http.Request) {
 	writeJSON(w, http.StatusOK, h.tuningSnapshot())
 }