Fix stuck gestures and scene graph races; honour commitVelocity

Gestures
- Cancel a captured gesture on lostpointercapture, on a new primary
  pointer-down, and when its component unmounts, so operations are
  never left stuck mid-transition. Bindings gain onLostpointercapture.
- Warn (console.warn) when navigate() fails or the scene rejects an
  operation; stay quiet when two recognizers race for one origin.
- OriginGesture and OriginGestureSurface props are reactive. Changes
  apply from the next pointer-down; recognizers are kept per list
  position so re-renders never interrupt a drag.
- Remove the legacy direction/edge/threshold/action gesture form
  (OriginGestureOptions, legacy OriginGesture props, MaybeOriginAction).

Scene
- Honour choreography commitVelocity (default 0.3, as before).
- Scene errors are OriginSceneError with a stable code.
- update() during settling now really catches an operation: the spring
  stops, and only the latest finish() decides the outcome.
- Fix graph corruption found by the new property tests, all present on
  main: replacements escaping a cancelled push, edges left dangling when
  their current target differs from the original one, revealed targets
  keeping operations after their back is cancelled, history pointing at
  removed entries after replace, visual cycles from back through an
  undecided replace, exposed nodes reactivated as active, and a cancel
  cascade that could empty the whole scene.

Tests
- Add property tests checking structural invariants after every step of
  random operation sequences and pointer streams (PROPERTY_SEEDS).
- Add recognizer tests for stuck gestures, warnings, reactive props,
  and commitVelocity. Drop the main-comparison suites; keep benchmarks.

Also fix the origins demo's two pre-existing type errors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Faarh2Ts6StJPcz2mRiHiR

packages/core-v2/verify/README.md

@@ -1,27 +1,20 @@
-# Differential verification
+# Benchmarks
 
-Checks a core-v2 implementation against an earlier one (by default `main`)
-by driving both with identical randomized inputs and requiring identical
-observable results after every step.
+Compares core-v2's performance against an earlier implementation (by default
+`main`).
 
 From the repository root:
 
 ```sh
 packages/core-v2/verify/setup-baseline.sh main   # extract into verify/.baseline/
-npx vitest run --config packages/core-v2/verify/vitest.config.ts
-SEEDS=50 npx vitest run --config packages/core-v2/verify/vitest.config.ts  # quicker
-ONLY=rewrite npx vitest bench --run --config packages/core-v2/verify/vitest.config.ts
 ONLY=baseline npx vitest bench --run --config packages/core-v2/verify/vitest.config.ts
+ONLY=rewrite npx vitest bench --run --config packages/core-v2/verify/vitest.config.ts
 ```
 
-- `scene.diff.ts` runs random `begin`/`update`/`finish`/`cancel`/animation
-  frame sequences against both scenes and compares nodes, operations, roots,
-  every node's composited style, interactivity, contexts, and every promise
-  result. It also compares action-helper output and the runtime export list.
-- `gesture.diff.ts` mounts both packages in Vue apps whose views install the
-  same gestures (builder definitions, legacy options, `OriginGesture`, and
-  `OriginGestureSurface`), dispatches identical random pointer streams, and
-  compares scene state and every navigation, start, and completion callback.
-- `scene.bench.ts` measures compositing, push/back cycles, and rendered
-  frames. Run each implementation in its own process with `ONLY=`; running
-  both in one process biases whichever runs second.
+`scene.bench.ts` measures compositing, push/back cycles, and rendered frames.
+Run each implementation in its own process with `ONLY=`; running both in one
+process biases whichever runs second.
+
+Behavioural verification lives with the unit tests: `src/property.test.ts`
+drives random operation sequences and pointer streams and checks the scene's
+structural invariants after every step. Set `PROPERTY_SEEDS` to run more.