Adopt retained HTML API with sharp rendering defaults

[petekp]

React components now keep their original HTML, state, focus and selection when moving between the page and a Three.js scene. Stationary text retains native display clarity.

Stacked on #32 (pkp/surface-api-refactor). Replaces that branch's public API and migrates the lab and Home/postcard consumers.

<Surface inScene={selected}>
  <Card />
</Surface>

Explicit Root/HTML/Scene/Mesh composition, SceneSurface, and element capture cover custom scenes and shaders. Named canvases are selected with canvasId, matching SurfaceCanvas id.

The review follow-up fixes keyed lists, shared capture readers, resizing anchors, preparation clipping, attribute validation, observer scheduling and Logo easing. The reported focus-loss sequence passes a permanent regression test.

Local verification	Result
Tests	1,528 passed across 117 files
Four typechecks, lint, package and lab builds	Passed
Rename verification	Six Chrome routing cases, four capability/fallback cases, and a live starter round trip passed
Postcard at rest, native DPR 2	Zero native/mesh pixel difference
Six postcard cycles	9.4 ms maximum unrecorded frame gap; 18.6 ms limit
Companion pixels	Zero boundary error; 0.000139 maximum spike; 0.5 limit
Scroll and form input	0.025 CSS px drift; original field retained at desktop/mobile widths
Placement, Knobs, Flight, Genie and Logo reruns	Passed

Review retained-node lifetime, pixel ownership and render-pass ordering. The aggregate postcard runner intermittently fails during recorder/Chrome teardown; individual probes pass. Evidence and dispositions record the verification limits and React Doctor warnings.