Three Phase 1D clusters in one commit (user opted for less iOS-sim
verification between each).
1.28 — `show_keyboard` / `hide_keyboard` use `#objc_call(u8)` against
`becomeFirstResponder` / `resignFirstResponder`. Compile-only; chess
startup doesn't reach the keyboard path, so the runtime side of this
cluster is a verification gap to backfill at the end of Phase 1D.
1.29 — `uikit_create_gl_context` migrates `alloc` / `initWithAPI:` /
`setCurrentContext:` and folds in the same `mainScreen.nativeScale`
read shape already migrated in 1.27. EAGL context creation runs on
launch, so this cluster IS runtime-exercised.
1.30 — `uikit_subscribe_keyboard_notifications` migrates the
`defaultCenter` + `addObserver:selector:name:object:` pair. First
standalone exercise of a 4-keyword selector through `#objc_call`.
Notification-center wiring runs at launch, so runtime-exercised.
Net -23 lines across the file.
iOS-sim chess regression smoke: app launches cleanly into a fresh
board state. Status-bar clearance, sharp rendering, and asset loading
all good — confirming clusters 1.25–1.27 still work alongside the new
ones.
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