Runtime super polish pass 2: runtime hardening and fixes

[RtlZeroMemory]

Summary

Runtime hardening pass for Rezi runtime layers, with targeted bug fixes and regression coverage.

Scope explicitly excludes Ink compatibility implementation work (packages/ink-compat/* unchanged).

What Was Fixed

1) Unicode-safe truncation in layout text measurement

• Fixed grapheme-splitting truncation in:
  • packages/core/src/layout/textMeasure.ts
• truncateWithEllipsis and truncateMiddle now truncate on grapheme boundaries instead of raw UTF-16 offsets.
• Added regression tests:
  • packages/core/src/layout/__tests__/textMeasure.truncate.unicode.test.ts

2) Focus-zone traversal correctness

• Fixed TAB traversal to skip empty zones (instead of clearing focus):
  • packages/core/src/runtime/focus.ts
• Fixed stale zone metadata after trap-driven focus reassignment (activeZoneId and zone memory now recomputed from final focus):
  • packages/core/src/runtime/focus.ts
• Added regression coverage:
  • packages/core/src/runtime/__tests__/focusZones.golden.test.ts

3) Native FFI boundary hardening (Rust addon)

• Added alignment validation for debug-query headers before casting to native header struct:
  • packages/native/src/lib.rs
• Fixed engineDebugGetPayload record-id parsing to reject out-of-range BigInt values (>= 2^64) instead of truncating.
• Added smoke regressions:
  • misaligned outHeaders rejection
  • oversized recordId rejection
  • in packages/native/scripts/smoke.mjs

4) CI coverage gap on Linux reduced e2e profile

• Added Linux reduced-profile e2e execution in CI:
  • .github/workflows/ci.yml
• Added workflow regression test:
  • scripts/__tests__/ci-workflow-linux-reduced-e2e.test.mjs

5) Bench dependency alignment

• ink is retained for benchmark scenarios.
• Benchmark package stays compatible with benchmark imports requiring ink.

Changed Files

• packages/core/src/layout/textMeasure.ts
• packages/core/src/layout/__tests__/textMeasure.truncate.unicode.test.ts
• packages/core/src/runtime/focus.ts
• packages/core/src/runtime/__tests__/focusZones.golden.test.ts
• packages/native/src/lib.rs
• packages/native/scripts/smoke.mjs
• .github/workflows/ci.yml
• scripts/__tests__/ci-workflow-linux-reduced-e2e.test.mjs
• packages/bench/package.json
• packages/bench/tsconfig.json
• package-lock.json

Validation

• npm run lint ✅
• npm run typecheck ✅
• npm run build ✅
• npm test ✅
• npm run test:e2e ✅
• npm run test:e2e:reduced ✅
• npm run test:native:smoke ✅
• npm -w @rezi-ui/native run build:native ✅
• cargo test (in packages/native) ✅
• node --test --test-concurrency=1 packages/core/dist/layout/__tests__/textMeasure.truncate.unicode.test.js packages/core/dist/runtime/__tests__/focusZones.golden.test.js ✅

Residual Notes

• No backend transport behavior changes were included in this PR.
• No Ink compatibility layer changes were included in this PR.