feat: draw the tracked hand skeleton over the camera

[Endika]

Answers the only question the UI could not: is it seeing me?

Until now, a hand that was tracked but whose shape was unknown looked exactly like a hand that was never detected — both produced silence. The user had no way to tell whether to move closer, fix the light, or change the handshape.

Three states, because "nothing happened" has three causes

Overlay	Status line	What to do about it
nothing drawn	Buscando la mano	get in frame
white skeleton	Mano detectada. Esa forma todavía no la conozco	change the handshape
violet skeleton	Leyendo	keep going

cover → contain

The video was cropping its sides, so a hand could be detected outside the visible area — the overlay would have drawn a skeleton onto a hand the user could not see. With contain, what you see is exactly what the model gets. The overlay projects landmarks through the same letterboxing, so the skeleton lands on the hand rather than near it.

MediaPipe 1.0.1

Also in this branch, superseding #2. Verified locally before merging rather than trusted: typecheck, build and all 43 tests pass, and the WASM filenames FilesetResolver looks for are unchanged across the major. That last one matters because scripts/copy-wasm.mjs stages the runtime from node_modules — the bump moves the JS and the WASM together, which is exactly why the WASM is not committed.

Camera still unverified under WSL2 (no device access); the projection maths is geometry, not something the synthetic-hand tests can exercise.