editor: unify walkthrough + viewer UI, crouch, screenshot pause (#529)

* feat(walkthrough): unify first-person and baked walkthrough UI into a shared HUD

The builder first-person overlay (crosshair, Exit Street View button, hints
card) and the baked-GLB walkthrough HUD were two divergent UIs. Extract the
GLB-style HUD (reticle, floor/room labels, Esc pill, interact prompt) into a
shared WalkthroughHud in packages/editor, feed it from FirstPersonControls via
a small useFirstPersonHud store (interact target each frame, floor/zone labels
sampled from the camera), and align FOV/projection handling with the baked
controller. The now-unused WalkthroughControls glide controller is removed
from packages/viewer (WALKTHROUGH_FOV moves to the GLB controller module).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(viewer-ui): shared ViewerControlsBar + ViewerSceneHeader for preview and embedders

Preview mode's ViewerOverlay was an older copy of the community viewer UI
(separate scan/guide/camera buttons, own render/theme/edges menus, 4-state
wall mode). Extract the community design into shared prop-driven components:
ViewerControlsBar (visibility, level/wall modes, display menu, walkthrough,
orbit/top view) and ViewerSceneHeader (back, project info, optional stats
slot, breadcrumb, levels card). ViewerOverlay is now a thin composition of
them. The display menu gains the edges submenu everywhere; the vestigial
translucent wall mode is dropped (a stale value renders as cutaway).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(walkthrough): hold-Ctrl crouch + P screenshot pause in both controllers

Crouch swaps the capsule for a short one (shrinks around the centre, so a
mid-jump crouch lowers the head and raises the feet — enough to thread window
openings), lowers the eye with a short lerp, and slows movement; standing back
up is gated on headroom via an upward raycast against the collider world.
Tuning constants live in the GLB controller module and are shared with the
editor first-person controller.

P releases the pointer lock without leaving the walkthrough so the cursor is
free for an OS screenshot (macOS region capture needs a movable pointer);
clicking the canvas re-locks and resumes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(walkthrough): crouched profile fits ~1 m openings

The float gap counts toward the effective obstacle height — the capsule rides
floatHeight (0.5 m) above the ground, so the old crouch spanned 0.5–1.3 m and
a 1.14 m opening still blocked it. Crouching now also lowers the float gap
(0.25 m) and uses a shorter capsule (0.7 m), for an effective 0.25–0.95 m
span; the stand-up headroom check grows to match.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(walkthrough): seamless screenshot pause — auto-release pointer lock on ⌘

Replace the P shortcut: macOS swallows the full ⇧⌘4 but the ⌘-down keystroke
still reaches the page, so the moment ⌘ (or PrintScreen) goes down while
locked the cursor is released without leaving the walkthrough — the native
screenshot flow just works, no user education. The HUD pill flips to "Click
to resume" (click-through, so the resuming click lands on the canvas) via a
new walkthroughSuspended flag on the viewer store, reset on lock/exit/unmount.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(walkthrough): screenshot pause is P again, advertised in the HUD

The ⌘ auto-release fired on every command combo and felt broken. Back to an
explicit P toggle, now discoverable: the HUD bottom shows a "P free cursor"
pill next to "Esc to exit", and while paused it flips to "Click or P to
resume · Esc to exit" (click-through so the resuming click lands on the
canvas). P re-locks as well as releasing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(walkthrough): freeze crouch during cursor pause; no editor hints in first person

While the P pause is active, Ctrl no longer toggles crouch — ⌃⇧⌘4 (clipboard
screenshot) was crouching the player mid-capture; the held state stays frozen
until resume. HelperManager now renders nothing in first-person mode, so the
Ctrl multi-select hint no longer pops over the walkthrough HUD (Ctrl is
crouch there).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* chore: biome formatting + pre-existing useOptionalChain fix in wall panel

The wall-panel lint error predates this branch (#526); fixed here to unblock
the quality gate.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/nodes/src/wall/panel.tsx

@@ -111,7 +111,7 @@ export default function WallPanel() {
   // renders at. `undefined` for walls with an explicit custom height.
   const planeBoundHeightMeters = useScene((s) => {
     const wall = selectedId ? (s.nodes[selectedId as AnyNodeId] as WallNode | undefined) : undefined
-    if (!wall || wall.type !== 'wall' || wall.height != null) return undefined
+    if (wall?.type !== 'wall' || wall.height != null) return undefined
     return resolveWallOpeningCeiling(wall, s.nodes)
   })