feat: separate mesh/SHX default fonts and preserve worker precision

[mlightcad]

Summary

• Introduce role-based default fallback fonts in FontManager: mesh (defaultMeshFont), primary SHX (defaultShxFont), and SHX big font (defaultShxBigFont), with indAndReplaceFont resolving by font type/role instead of a single defaultFont.
• Add setDefaultFonts(mesh, shx, shxBig) on UnifiedRenderer / main-thread / Web Worker renderers; initialization loads all three defaults.
• Fix Web Worker MText serialization/reconstruction so large drawing insertion coordinates stay on the root group transform while glyph geometry remains local (avoids float precision loss in vertex buffers).
• Fix decoration line geometries to use explicit indices; ensure unindexed line geometries are indexed before merge.
• Update the example app with separate default font dropdowns and demo cases for missing inline/style fonts.
• Bump @mlightcad/mtext-renderer to 0.11.0.

Test plan

• Run
  x test mtext-renderer (or package test script) and confirm ontManager, mtext.processor, mtext.anchor, and webWorkerRenderer.precision tests pass.
• Run the example app; verify mesh / English SHX / big SHX default selectors reload fonts and re-render.
• In the example font demo, confirm missing mesh/SHX inline fonts and missing text-style primary/big fonts fall back to the configured defaults.
• Render MText at large world coordinates in Web Worker mode and confirm position/anchor match main-thread rendering (no jitter or offset).

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