feat: /examples section (World globe + Flat Map) + landing lighting + render perf

[apresmoi]

What

Adds an /examples section to the website and folds in the landing-globe lighting work and a couple of render-path improvements that came out of building it.

/examples section

• New left sidebar (World / Flat Map) with active-state highlighting.
• /examples → redirects to /examples/world.
• /examples/world — the ASCII Earth globe (former local /map), drag to orbit, scroll to zoom.
• /examples/flatmap — the iso pan/zoom Web-Mercator terrain map (former local /flatmap) with the control dock + country labels.
• Examples link added to the top nav.

Landing

• Dropped realSunLight on the hero (the real-time terminator left the visible face mostly on the night side → dark/"weirdly contrasted").
• New per-demo light override prop on GlyphDemo ({ direction, intensity, ambient }) so the hero gets a bright, even fixed key without changing the global default for docs demos.

Render (@glyphcss/core rasterizer / scene)

• Cache lit colors per render + memoize hex→rgb parsing (the color path was ~doubling rasterize time at high poly counts).
• Measure cell height from a multi-line probe instead of a single glyph — fixes the scene visually shrinking at line-height < ~0.8.

Data weight

The example pages fetch pre-baked tile JSON at runtime. The full pyramids were 276 MB, so they're capped to what these demos actually need:

• Globe: z0–z1 (~11 MB) — decorative orbit view, deep zoom isn't worth the weight.
• Flat map: z0–z3 (~16 MB) — the interactive demo keeps good zoom depth.
• Total committed: ~27 MB, largest single file 2.3 MB.

LOD selection + max-zoom are capped in code so the pages never request a dropped level (verified: aggressive zoom → zero /data/ 404s). Deeper levels remain regenerable from etopo/gadm via the bake scripts.

CI / build notes

• pnpm test (294) and pnpm build both pass; /examples/* routes generate.
• Build never touches etopo/gadm — those are local-only bake inputs, not build inputs.
• gdal-async is intentionally not a package.json dependency (only the manual bake-labels.mjs uses it); the transient-install command is documented in the script header.

Notes

• No public package API change → no React/Vue mirror needed (the light prop is on the website's GlyphDemo, not the published packages).