TextStyle completeness: add strikethrough/overline/blink with merge+encoding hardening

[RtlZeroMemory]

Summary

• add strikethrough, overline, and blink to TextStyle and style presets
• extend ResolvedTextStyle and mergeTextStyle to merge/inherit all 8 boolean attrs with tri-state semantics
• expand BASE_BOOL_STYLE_CACHE keyspace handling for 8 attrs (65536 direct-addressed entries)
• update drawlist style encoding in v1/v2 builders to pack attrs on bits 0..7 (strikethrough=5, overline=6, blink=7)
• include new attrs in runtime text style equality checks used by commit diffing
• update partial drawlist style-key test helper to track new attrs
• bump vendored Zireael engine to v1.3.5 (d551156) so backend SGR emission supports strikethrough, overline, and blink

Tests

• add and expand deterministic style tests:
  • packages/core/src/widgets/__tests__/style.attributes.test.ts
  • packages/core/src/widgets/__tests__/style.merge.test.ts
  • packages/core/src/drawlist/__tests__/builder.style-encoding.test.ts
• exhaustive attr encoding checks for all 256 boolean masks across drawlist builders
• merge/cache correctness checks across all 8 attrs (inherit/override/deep chains/cache separation)
• full repo validation: npm run lint, npm run typecheck, npm run build, node scripts/run-tests.mjs

Docs

• update docs/guide/styling.md
• add docs/guide/text-style-internals.md with bit layout, merge semantics, cache details, and backend support status

Why

This closes style-pipeline gaps for missing text attributes from definition through merge, drawlist encoding, and backend SGR emission, with broad regression coverage for future changes.

[chatgpt-codex-connector]

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