v0.1.2: transport buttons fill their bubble as equal tap targets

Prev/play/next (and shuffle) used to hug their ~20px glyphs in the middle
of the 62px rounded box, so most of the bubble was dead space. _box() now
takes split=True: the buttons tile the bubble interior in equal shares,
expanding to the (tightened) margins with the glyph centered in each.
Minimum button widths keep the bubbles at their old footprint — no bigger,
no smaller. Round 21 tests cover the equal split, vertical fill, edge
spans, and the preserved footprint.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

TASKS.md

@@ -3,7 +3,17 @@
 Legend: `[ ]` todo · `[~]` in progress · `[x]` done.
 When a round closes, move its finished items to `tasks-done.md`.
 
-## Round 20 (current) — Ctrl+I save hang on the Debian machine (v0.1.1)
+## Round 21 — transport buttons fill their bubble (v0.1.2)
+
+Plan reference: `~/.claude/plans/tap-targets-on-the-snazzy-minsky.md`.
+Tests in `tests/test_round21.py`. Fix-only round → patch bump **0.1.2**.
+
+- [x] Prev/play/next (and shuffle) tap targets now tile their rounded box:
+      `_box(split=True)` in `gui/transport.py` gives each button an equal,
+      full-height share of the bubble with the glyph centered; minimum
+      button widths keep the bubbles at their old footprint (no bigger).
+
+## Round 20 — Ctrl+I save hang on the Debian machine (v0.1.1)
 
 Plan reference: `~/.claude/plans/i-m-having-some-trouble-eager-gosling.md`.
 Tests in `tests/test_round20.py`. Fix-only round → patch bump **0.1.1**.