feat: CLI observability + fix studio save failures on JS-created elements (#1091)

* feat(core): add probeElementInSource for source-existence checks

* feat(core): add probe-element endpoint for source-existence checks

* feat(studio): gate editing capabilities on source existence

* fix(studio): enrich save_failure telemetry with target details

* feat(studio): async selection resolution with source probe

Make `resolveDomEditSelection` async and wire a `probeSourceElement` call
into the selection path so elements generated by scripts (not present in the
source HTML) are detected early and have all edit capabilities disabled with
a clear reason message ("This element is generated by a script and cannot be
edited visually.").

Part A – core probe logic:
- `domEditingLayers.ts`: `resolveDomEditSelection` is now async; calls
  `probeSourceElement` (POST /api/projects/:id/file-mutations/probe-element/:file)
  when `projectId` is supplied and the element has a stable id/selector.
  `existsInSource: false` flows into `resolveDomEditCapabilities`, which
  disables all write capabilities with the appropriate reason.
- `domEditingLayers.ts`: `refreshDomEditSelection` promoted to async.
- `files.ts`: new `probe-element` route; extracted `resolveProjectPath`,
  `resolveFileMutationContext`, `writeIfChanged`, and `parseMutationBody`
  helpers to eliminate repeated boilerplate across remove/patch/probe handlers.

Part B – caller propagation (all eight consumer sites):
- `useDomSelection.ts`: `buildDomSelectionFromTarget`,
  `resolveDomSelectionFromPreviewPoint`,
  `buildDomSelectionForTimelineElement`, `handleTimelineElementSelect`,
  `refreshDomEditSelectionFromPreview`, and
  `refreshDomEditGroupSelectionsFromPreview` all made async; `projectId`
  forwarded into `resolveDomEditSelection`.
- `useDomEditCommits.ts`, `useDomEditTextCommits.ts`: updated
  `buildDomSelectionFromTarget` parameter type; added `await` at call sites.
- `useDomEditSession.ts`: inner `syncSelectionFromDocument` made async; fire
  with `void` to satisfy the surrounding effect.
- `usePreviewInteraction.ts`: `handlePreviewCanvasMouseDown` and
  `handlePreviewCanvasPointerMove` made async (React ignores handler return
  values, so this is safe).
- `useStudioUrlState.ts`: deferred `buildDomSelectionFromTarget` call
  converted to `.then()` chain with `void` prefix so the effect stays sync.
- `LayersPanel.tsx`: `seekToLayer`, `handleSelectLayer`, and
  `handleLayerHover` made async.
- `DomEditOverlay.tsx` / `useDomEditOverlayGestures.ts`: `onCanvasPointerMove`
  return type widened to `Promise<DomEditSelection | null>`; pointer-down
  handler falls back to `hoverSelectionRef.current` (always populated by a
  prior hover) instead of awaiting the async move callback inline.

Part C – test and tooling fixes:
- `lefthook.yml`: filesize hook shell loop explicitly skips `*.test.ts/tsx`
  files as a guard against a lefthook v2.1.6 bug where `exclude` patterns are
  not applied to `{staged_files}` in shell scripts.
- `domEditing.test.ts`: all `it()` blocks calling `resolveDomEditSelection`
  made async with `await`.
- `DomEditOverlay.test.ts`: mock updated to return `Promise.resolve(selection)`
  and `hoverSelection` pre-seeded so pointer-down test works with the new
  hover-first path.
- `studioUrlState.test.ts`: `buildDomSelectionFromTarget` mocks wrapped in
  `Promise.resolve()`; seek/selection hydration test made async with
  `await act(async () => { await Promise.resolve(); })` to flush microtasks.

* feat(cli): add global error handlers for crash telemetry

Register process-level uncaughtException and unhandledRejection handlers
that fire trackCliError so unhandled crashes are captured in telemetry.
Add the trackCliError function to events.ts and re-export it from the
telemetry barrel.

* feat(cli): track per-command success/failure and duration

* test(core): add integration test for JS-created element probe scenario

* fix: address PR review feedback

- uncaughtException handler now calls process.exit(1) after flushing
- cli_command_result uses real exit code from process "exit" event
- drop stack_trace from cli_error (contains filesystem paths)
- skip source probe during hover — only probe on click/selection
- format .fallowrc.jsonc

* fix(cli): restore stack_trace in cli_error telemetry

* fix(cli): use captured module refs in exit handlers instead of dead import()

packages/studio/src/components/editor/DomEditOverlay.tsx

@@ -43,7 +43,7 @@ interface DomEditOverlayProps {
   onCanvasPointerMove: (
     event: React.PointerEvent<HTMLDivElement>,
     options?: { preferClipAncestor?: boolean },
-  ) => DomEditSelection | null;
+  ) => Promise<DomEditSelection | null>;
   onCanvasPointerLeave: () => void;
   onSelectionChange: (
     selection: DomEditSelection,
@@ -195,9 +195,8 @@ export const DomEditOverlay = memo(function DomEditOverlay({
   const handleOverlayPointerDown = (event: React.PointerEvent<HTMLDivElement>) => {
     if (!allowCanvasMovement || event.button !== 0) return;
     if (event.shiftKey) {
-      const candidate =
-        onCanvasPointerMoveRef.current(event, { preferClipAncestor: false }) ??
-        hoverSelectionRef.current;
+      // Use the already-updated hover selection rather than re-resolving async
+      const candidate = hoverSelectionRef.current;
       if (!candidate) return;
       event.preventDefault();
       event.stopPropagation();
@@ -211,9 +210,7 @@ export const DomEditOverlay = memo(function DomEditOverlay({
     const target = event.target as HTMLElement | null;
     if (target?.closest('[data-dom-edit-selection-box="true"]')) return;
 
-    const candidate =
-      onCanvasPointerMoveRef.current(event, { preferClipAncestor: false }) ??
-      hoverSelectionRef.current;
+    const candidate = hoverSelectionRef.current;
     if (!candidate?.capabilities.canApplyManualOffset) return;
 
     const overlayEl = overlayRef.current;