docs(examples): Feature Catalog blocks for the v1.8 surface (paths, SVG beta, debug overlay)

[DemchaAV]

Adds four self-documenting blocks to the flagship Feature Catalog (now 23 blocks / 7 pages):

• Vector paths — solid + dashed(6, 3) native Bézier waves via addPath.
• SVG path import (beta) — Material heart from a raw d string through SvgPath.parse.
• SVG icons (beta) — six svgrepo icons (apple, headphones, cart, camera, starfish, toolbox) on tile cards; the code panel teaches the LayerAlign-anchor centring pattern (fixed card box + tight-box icon stack).
• Debug overlay — .debug(DocumentDebugOptions.nodeLabels()) switch, prose-style like the Page-chrome block.

CHANGELOG: catalog bullet updated (19→23 blocks, 6→7 pages).

Deliberately not regenerated here: assets/readme/examples/feature-catalog.pdf — #175 already modifies that binary; I'll regenerate it once the queue (#172→#173→#176, #174, #175) is merged and this PR is retargeted to develop, so the asset lands exactly once with the jpg hero.

Stacked on #176 (needs the gallery's /icons/*.svg resources).