docs: record native canvas selection gate

docs/studio-canvas-selection-native-feasibility.md

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+# Studio Canvas Selection Native Feasibility
+
+## Gate 0 Result
+
+Status: **NO-GO / blocked**
+
+The full non-invasive Studio canvas selection architecture must not be implemented yet.
+Gate 0 did not produce a GO result because:
+
+- Android executed and measured, but the proposed native instrumentation boundary was not measurable.
+- iOS could not be executed in this environment because Xcode has an iOS Simulator SDK/runtime mismatch.
+
+This report is intentionally limited to Gate 0. It does not approve a web-only fallback and does
+not approve implementing the full selection architecture.
+
+## Probe Scope
+
+The disposable probe was created under:
+
+```text
+/private/tmp/studio-canvas-gate0
+```
+
+It rendered baseline and instrumented versions of:
+
+- `Stack`
+- `Inline`
+- `Grid`
+- `Text`
+- `Card`
+- `Button`
+- nested Runtime-node-shaped boundaries
+
+The proposed native boundary used:
+
+```tsx
+<View collapsable={false} pointerEvents="box-none" style={{ display: 'contents' }}>
+  {children}
+</View>
+```
+
+The probe measured:
+
+- native handles with `findNodeHandle`
+- bounds with `measureInWindow`
+- baseline vs instrumented container and leaf geometry
+- selected chrome overlay geometry
+- coordinate hit-testing from measured bounds for nested Runtime nodes
+
+Compilation and type support were not treated as evidence.
+
+## Android Evidence
+
+Platform executed:
+
+```text
+Pixel_8_Pro_API_34-ext11
+Android emulator serial: emulator-5554
+React Native: 0.81.5
+Expo: 54.0.36
+```
+
+Commands executed:
+
+```bash
+emulator -avd Pixel_8_Pro_API_34-ext11 -no-window -no-audio -no-snapshot -gpu swiftshader_indirect
+adb shell getprop sys.boot_completed
+expo prebuild --platform all --no-install
+expo run:android
+```
+
+Android build, install, and JS execution completed. The probe emitted:
+
+```text
+GATE0_RESULT ... "platform":"android" ... "pass":false
+```
+
+Important measured result:
+
+```json
+{
+  "platform": "android",
+  "uiManagerAvailable": true,
+  "cases": [
+    { "type": "Stack", "boundaryMeasurable": false, "boundary": { "width": 0, "height": 0 } },
+    { "type": "Inline", "boundaryMeasurable": false, "boundary": { "width": 0, "height": 0 } },
+    { "type": "Grid", "boundaryMeasurable": false, "boundary": { "width": 0, "height": 0 } },
+    { "type": "Text", "boundaryMeasurable": false, "boundary": { "width": 0, "height": 0 } },
+    { "type": "Card", "boundaryMeasurable": false, "boundary": { "width": 0, "height": 0 } },
+    { "type": "Button", "boundaryMeasurable": false, "boundary": { "width": 0, "height": 0 } },
+    {
+      "type": "NestedRuntime",
+      "boundaryMeasurable": false,
+      "boundary": { "width": 0, "height": 0 }
+    }
+  ],
+  "hitTest": {
+    "expected": "nested-child",
+    "actual": "nested-child",
+    "passed": true
+  },
+  "selectedChrome": {
+    "selectedBounds": { "width": 0, "height": 0 },
+    "overlayBounds": { "width": 4, "height": 4 },
+    "passed": false
+  }
+}
+```
+
+Android conclusion:
+
+- Native handles existed for the boundary nodes.
+- The boundary was not meaningfully measurable: every instrumented boundary measured `0x0`.
+- Coordinate hit-testing only passed because both nested boundaries collapsed to a zero-size point;
+  that is not sufficient for real canvas selection.
+- Selected chrome could not align to a meaningful selected node rectangle.
+
+Android is therefore **NO-GO** for the proposed boundary.
+
+## iOS Evidence
+
+Available simulator query succeeded with escalation:
+
+```bash
+xcrun simctl list devices available
+```
+
+Available devices included bootable iOS simulators, and this simulator was booted:
+
+```text
+iPhone 16 Pro (19CA5E47-EB9E-4B7E-B533-29E137F08954) (Booted)
+```
+
+The iOS simulator did not have Expo Go installed:
+
+```bash
+xcrun simctl get_app_container booted host.exp.Exponent
+```
+
+Result:
+
+```text
+No such file or directory
+```
+
+A disposable native iOS shell was generated and CocoaPods installed, but Xcode could not build to
+any simulator destination:
+
+```bash
+expo prebuild --platform all --no-install
+expo run:ios --device 19CA5E47-EB9E-4B7E-B533-29E137F08954
+expo run:ios --device "iPhone 16 Pro"
+xcodebuild -workspace /private/tmp/studio-canvas-gate0/ios/StudioCanvasGate0.xcworkspace \
+  -scheme StudioCanvasGate0 -showdestinations
+```
+
+Xcode result:
+
+```text
+Unable to find a destination matching the provided destination specifier
+Ineligible destinations for the "StudioCanvasGate0" scheme:
+  { platform:iOS, name:Any iOS Device, error:iOS 26.5 is not installed. }
+```
+
+Installed SDKs/runtimes:
+
+```text
+xcodebuild -showsdks:
+  iOS Simulator SDK 26.5
+
+xcrun simctl list runtimes:
+  iOS 18.0
+  iOS 18.5
+  iOS 26.2
+```
+
+iOS conclusion:
+
+- iOS did not execute the React Native probe.
+- The blocker is local environment availability, not TypeScript or source compatibility.
+- Manual iOS Gate 0 evidence is required before implementing the full architecture.
+
+## Required Next Step
+
+Do not implement the full canvas selection architecture until both conditions are met:
+
+1. Android has a revised native boundary or measurement strategy that returns meaningful non-zero
+   bounds while preserving layout transparency for every required fixture.
+2. iOS executes the same native feasibility probe, or an equivalent committed probe, on a simulator
+   or device and records layout transparency, measurability, selected chrome, and coordinate
+   hit-testing evidence.
+
+Native hover/focus chrome remains capability-driven. Lack of hover on touch-only platforms must not
+fail the gate, and Studio must not add artificial focusability or authored-component handlers.