test: backfill Ink-parity coverage gaps (suite as a superset of Ink) (#130)

Regression tests for behaviors the audit found correct-but-unpinned, so the
suite is a strict superset of Ink:
- A07: two <Static> regions both render (the additive divergence)
- B04: Static render-prop index = absolute index across appends; container
  vertical padding adds blank rows to the static frame
- B11: lazy raw-mode acquire/release under rawMode:'auto' (the path the
  'always' default masks)
- B19: child useCursor unmount emits the cursor-hide escape (stream-level)
- B20: animation interval 0/negative clamps to 1ms (normalizeInterval unit) and
  advances without busy-hang
- B21/B28: INK_SCREEN_READER env auto-detection + useIsScreenReaderEnabled
  true-path (env tests isolated in a *.sequential file per the global-state rule)
- B29: renderToString serves useCursor/usePaste/useTerminalSize/useAnimation/
  useBoxMetrics as inert no-ops (don't throw)
- B30: dedicated columnGap/rowGap props + their removal-reset

Test-only; no production changes. Codex-reviewed for non-vacuousness, Ink
correctness, and process-global isolation.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/runtime-tests/unit/animation-scheduler.sequential.test.ts

@@ -14,6 +14,7 @@ describe.sequential("normalizeInterval", () => {
   test("clamps and defaults", () => {
     expect(normalizeInterval(50)).toBe(50);
     expect(normalizeInterval(0)).toBe(1);
+    expect(normalizeInterval(-5)).toBe(1);
     expect(normalizeInterval(-10)).toBe(1);
     expect(normalizeInterval(undefined)).toBe(100);
     expect(normalizeInterval(Number.NaN)).toBe(100);