Document the Library tab in the changelog and README

Claude-Session: https://claude.ai/code/session_01H8VxUX4ckjU3vRF5M4L5FV

README.md

@@ -13,10 +13,18 @@ your own iCloud Drive.
   (the **Morning Wake-Up** starter split ships this way). Built-in starter splits
   (Upper Body / Core / Lower Body machine routines, plus an equipment-free
   **Bodyweight Core** circuit with its own warm-up) appear automatically on first
-  launch; editing one makes it your own copy, and deleted starters can be restored
-  from Settings. Any exercise can be duplicated and renamed for this routine only
+  launch and wear a **Starter** badge; editing one makes it your own copy. Any
+  exercise can be duplicated and renamed for this routine only
   (its figure and guide still come from the original) — build an interval routine
   like a treadmill's Warmup / Brisk Walk / Cooldown from one library exercise.
+- **Library tab** — a dedicated tab for managing it all: drag routines into your
+  own order (the Today board and pickers follow it), duplicate any routine with a
+  swipe, see each routine's usage at a glance (last trained, workouts completed,
+  scheduled days — with a warning if you delete a routine that schedules still
+  reference), and browse a **starter gallery** that previews every built-in
+  routine — including deleted ones — and re-adds them individually or all at
+  once. The exercise library and the add-exercise picker are grouped by category
+  and searchable by name, category, or muscle.
 - **Exercise library** — a bundled library of 67 exercises to populate your
   splits, authored in `Exercise Library/` with per-exercise setup, cues,
   mistakes, progressions, and an anatomically-rigged 3D stick-figure visual