fix(workouts): resolve duplicate clusters the same way on every surface

The cross-source picker anchors each duplicate cluster on its first start,
so which cluster a workout lands in depends on the workouts around it. The
detail route still read the old fixed five-minute clock slot, and every
other reader handed the picker only the rows of its own range. The detail
of a twin that straddled a slot boundary declared itself canonical while
the list hid it, and runs at 09:58, 10:02 and 10:06 were grouped one way by
a read starting at 09:55 and another by a read starting at 10:00.

Every reader that decides which workout is canonical (list, detail and its
previous session, activity calendar, day view, doctor report, Coach,
briefing and correlation blocks, strain, per-sport context, the activity
insight's history, the batch write) now reads through one windowed reader.
It reads a duplicate window past the end of the range and reaches back
until every sport in the range starts at a workout that is an anchor
whatever came before it, then picks over everything read and keeps the
rows that start inside the range. The per-sport baseline and the insight
history leave out the whole cluster of the current session instead of the
row alone, which left its twin behind as a session of its own. The batch
write clusters its rows together with the stored workouts around them and
drops only a row that loses to another row of the same batch.

A property test checks the windowed read against a whole-history read for
random dense histories and ranges; route tests pin list, detail, deep link,
previous session and the batch write against the database.

src/__tests__/baselines/source-function-lines.json

@@ -1,7 +1,7 @@
 {
   "$comment": "Production functions over 200 lines, keyed \"file :: name\", and their length. Maintained by src/__tests__/source-size-ratchet.test.ts.",
   "count": 411,
-  "total": 148369,
+  "total": 148324,
   "entries": {
     "app/achievements/page.tsx :: AchievementsPage": 206,
     "app/api/admin/backups/upload/route.ts :: apiHandler(arg)": 314,
@@ -64,8 +64,8 @@
     "app/api/sync/changes/route.ts :: apiHandler(arg)": 427,
     "app/api/user/ai-provider/route.ts :: apiHandler(arg) #2": 252,
     "app/api/withings/callback/route.ts :: apiHandler(arg)": 247,
-    "app/api/workouts/[id]/route.ts :: apiHandler(arg)": 313,
-    "app/api/workouts/batch/route.ts :: postBatch": 722,
+    "app/api/workouts/[id]/route.ts :: apiHandler(arg)": 297,
+    "app/api/workouts/batch/route.ts :: postBatch": 709,
     "app/auth/login/page.tsx :: LoginPage": 576,
     "app/auth/register/page.tsx :: RegisterPage": 285,
     "app/coach/conversations/page.tsx :: CoachConversationsBody": 249,
@@ -287,7 +287,7 @@
     "lib/ai/anthropic-client.ts :: generateCompletion": 294,
     "lib/ai/coach/cycle-snapshot.ts :: buildCycleSnapshotBlock": 218,
     "lib/ai/coach/glp1-snapshot.ts :: buildGlp1SnapshotBlock": 218,
-    "lib/ai/coach/snapshot.ts :: buildCoachSnapshotImpl": 898,
+    "lib/ai/coach/snapshot.ts :: buildCoachSnapshotImpl": 882,
     "lib/ai/coach/tools/loop.ts :: runCoachToolLoop": 438,
     "lib/ai/coach/turn/model.ts :: runTurnModel": 560,
     "lib/ai/coach/turn/pipeline.ts :: runTurn": 274,