fix(sdk): click-to-pick fills its view, the camera-controls proof waits for the lock (#527)

[pasquelin]

Closes #527

What changed

The examples proof's remaining causes, fixed where they live.

• click-to-pick is framed closer, camera (0,4,6) → (0,3.2,4.8). It drew 9.3 % on WebGL2 against a bound of 10 %: six small shapes on a thin grid. The ring now fills the view on both backends. scripts/docs-examples-draw.test.ts lists it at the tenth on both backends.
• native-camera-controls now waits for the pointer lock as an event (pointerLocked, tests/browser/support/cameraControlsPage.ts), never by a fixed delay; a released or refused lock rejects. It spends the one move the head drops by design (Engine fixes from the review of 24 Sept.: a failed resolution, lost children, lights, device loss, one raycast #385), then counts four moves out and four back. It checks the pose before the image, each with its own message.
• default-backend names the machine that drew nothing, with its frame counters. Its cause is tracked on Audit of #438: a second scene model in the engine, witness code and Three.js wording left in the package #457 (CTO).
• Shipping elsewhere, per the CTO: the WebGL2 materials (lambert, phong, toon, normal and matcap for the-material-family, create-and-dispose, toon-shading and a-matcap-sculpture) ship with the lighting lead's WebGL2 draws lambert, toon and matcap materials, never a blank page #772, with one source for WGSL and GLSL. Audit of #389: anisotropy capped at 8 taps, parked examples, witness in engine comments #443 already drew the non-image textures.
• Already on develop: the physics set derived from the pages (Joints and vehicles 5/5: the roller coaster rides its track on a path joint #503) and the sparse test on literal shares (save-the-scene is understood by playing it, and physics examples share one readout #717).

Image change, accepted by the CTO: click-to-pick's framing, on both backends. No engine code changes.

For the measurer: the closer framing may hide a WebGL2 divergence, grid lines under a pixel drawn with no antialiasing. Record WebGPU's share next to WebGL2's.

Proof

• pnpm run build, then pnpm run check:changed: 15 pass, 0 fail.
• pnpm run test:changed: 15 pass, 0 fail.
• pnpm run validate --group typescript: pass.
• pnpm run validate --group quick: formatting passes. check-file-lines fails on backend/types.ts (202 lines) and world/session/backends.ts (201 lines), both identical to develop after feat(fluids): one GPU particle pool, stepped by a WebGPU compute pass; WebGL2 refused by name until #759 (#420) #776; this branch does not touch them.
• node scripts/check-pr-size.ts: 49 hand-written lines added.
• camera/controls/firstPerson.test.ts: the dropped-move test also turns the head back in four moves. The head returns to where it started, and a lost or counted extra move fails it.
• Browser proofs, run by the measurer after the merge: node tests/browser/test-gpu.ts scripts/docs-examples.browser.ts and tests/browser/renders/native-camera-controls.browser.ts.

Local review before push

• Simplification pass: a second, fresh run of the real simplify skill on the remaining diff, with 4 agents (reuse, simplification, efficiency, altitude). The efficiency agent found nothing to change. Fixed: the new first-person test copied the dropped-move test, so it is folded into it as "a turn and its reverse return the head"; default-backend's loop runs over the runs and names each machine from the run itself; pointerLocked has one settle for both events and still waits on the event, as the CTO's To-do asks. Kept: page.waitForFunction for the lock (the To-do asks for an event), and default-backend's message (the CTO's decision, cause on Audit of #438: a second scene model in the engine, witness code and Three.js wording left in the package #457).
• Correctness review: a second, fresh run of the real code-review --fix skill, with five findings and no fix needed. Skipped: a lock refused before pointerLocked starts listening hangs until the harness timeout ends the run rather than failing; listening before the press would change a Chrome proof the reviewer cannot run. Also skipped: a move Chrome might send when it grants the lock, which only the measurer's run can confirm; the sparse-list entry, which does not guard the framing (the examples proof does); and two robustness notes that hold under today's asserts and single-canvas page.
• Acceptance list: every item of Every example renders an image in the examples proof #527 is delivered or placed by the CTO (materials WebGL2 draws lambert, toon and matcap materials, never a blank page #772, default-backend's cause Audit of #438: a second scene model in the engine, witness code and Three.js wording left in the package #457, physics set Joints and vehicles 5/5: the roller coaster rides its track on a path joint #503, sparse test save-the-scene is understood by playing it, and physics examples share one readout #717). Closes #527. Nothing under webgl/, host/surfaceGate.ts, scene/surfaceModel.ts or the WGSL differs from develop. The dropped-move test fails if one move of the reverse is lost or the jump counts (rounding to 6 digits). The framing is an image change accepted by the CTO, proven by the measurer.

Not proven / left out

• Not proven without a browser: click-to-pick at or above the tenth on both backends, and native-camera-controls passing.
• Left out: the WebGL2 materials (WebGL2 draws lambert, toon and matcap materials, never a blank page #772, per the CTO) and default-backend's 0 px cause (Audit of #438: a second scene model in the engine, witness code and Three.js wording left in the package #457).

Lead verification

• Every example draws, click-to-pick: delivered in site/examples/click-to-pick.html (camera (0,4,6) → (0,3.2,4.8), framed to fill the view, accepted by the CTO) and scripts/docs-examples-draw.test.ts:52-61 (it keeps the tenth on both backends); proved by a sparse example is declared by name and backend under the tenth; every other keeps the tenth and by the measurer on this branch: WebGPU 0.168, WebGL2 0.151, no error, no WebGL2 grid-line loss.
• Every example draws, native-camera-controls: delivered in tests/browser/support/cameraControlsPage.ts:107 (pointerLocked, the lock awaited as an event, a refusal named) and tests/browser/renders/native-camera-controls.browser.ts:127 (one move spent for the drop of Engine fixes from the review of 24 Sept.: a failed resolution, lost children, lights, device loss, one raycast #385, the pose checked before the image); proved by the first move after the lock is granted is dropped: the cursor jump never turns the head, and a turn and its reverse return the head and by the measurer: the proof passes 2 of 2 at d172bb0.
• Every example draws, ride-a-roller-coaster in the physics set and the sparse test that could not fail: already delivered on develop (Joints and vehicles 5/5: the roller coaster rides its track on a path joint #503, save-the-scene is understood by playing it, and physics examples share one readout #717).
• Every example draws, the WebGL2 materials (lambert, phong, toon, normal, matcap): ship with lighting WebGL2 draws lambert, toon and matcap materials, never a blank page #772 (CTO decision), not in this pull request.
• Every example draws, default-backend 0 px: moved to Audit of #438: a second scene model in the engine, witness code and Three.js wording left in the package #457 (CTO decision); here only its failure message names each machine's counters (tests/browser/renders/default-backend.browser.ts), whose first run is on Audit of #438: a second scene model in the engine, witness code and Three.js wording left in the package #457.
• Proof, the examples proof passes on the measurer's machine: the items above measured on this branch; the full proof after the merge.
• rounds: 2 (coder ↔ reviewer), plus a second fresh reviewer (CTO rule).
• Whole promise: every item delivered here or placed by the CTO.
• Tests that bite: the dropped-move test fails on a lost or extra move; the sparse test on a missing tenth.
• No image loss: click-to-pick's framing, accepted by the CTO before this pull request; nothing else drawn changes (no file under webgl/, host/surfaceGate.ts, scene/surfaceModel.ts or the WGSL differs from develop).
• Reuse: pointerLocked searched (no lock-wait helper existed; waitForFunction would poll and lose the refusal); machineLabel reused.
• Docs: none changed.
• Path: in review set; to measure after the merge (the click-to-pick thumbnail, the full examples proof). Streaming without holes: rules and objectives for geometry, memory and shadows #483 checklist and CONTRIBUTING.md §Streaming, memory and shadows: no engine path touched.