refactor: delete orphan declarations flagged by fallow (#949)

* ci: run fallow audit in lefthook pre-commit

Mirrors the same `fallow audit --base ... --fail-on-issues` check that
runs in CI, but locally against HEAD so issues surface at commit time
instead of after the push round-trip.

Scoped to `packages/**` source files via the glob — non-code edits
(README, docs, top-level configs) skip the hook entirely.

Measured locally: ~5s in parallel with the existing lint/format/typecheck
checks. Doesn't extend wall-clock time because typecheck (~11s) is the
long pole, and lefthook runs commands in parallel.

The default `--gate new-only` means inherited findings don't block the
commit — same gate behavior as CI, so local pre-commit and PR audit
agree.

* refactor: delete orphan declarations flagged by fallow

After fallow's auto-fix de-exports unused symbols, oxlint surfaces them
as no-unused-vars. This PR deletes those orphan declarations outright.

Biggest cleanup: studio/src/icons/SystemIcons.tsx shrinks from 132 to 57
lines — 33 unused icon wrappers and their phosphor-icon imports deleted.

Other deletions across 14 more files covering paired getter/setters,
helper functions, dead env constants, internal components with no
callers, and cascading unused imports.

Cascade-causing files held back for follow-up PRs: renderOrchestrator
barrel of captureCost re-exports, telemetry/portUtils/remote barrels,
Button.tsx + ui/index.ts (would orphan whole file), studioMotion
type re-exports.

Test plan: typecheck clean across 8 packages, oxlint + oxfmt clean,
fallow audit exit 0 (remaining findings inherited), cli + studio
vitest suites pass.

packages/studio/src/components/editor/domEditingElement.ts

@@ -12,9 +12,7 @@ import type {
 import {
   buildStableSelector,
   escapeCssString,
-  findClosestByAttribute,
   getElementDepth,
-  getPreferredClassSelector,
   getSelectorIndex,
   getSourceFileForElement,
   isHtmlElement,
@@ -60,7 +58,7 @@ function isEmptyVisualContainer(el: HTMLElement): boolean {
   return true;
 }
 
-export function hasRenderedBox(el: HTMLElement): boolean {
+function hasRenderedBox(el: HTMLElement): boolean {
   const rect = el.getBoundingClientRect();
   if (rect.width <= 1 || rect.height <= 1) return false;
   if (!isElementComputedVisible(el)) return false;
@@ -324,7 +322,3 @@ export function getDirectLayerChildren(
       isHtmlElement(child) && getDomLayerPatchTarget(child, options.activeCompositionPath) !== null,
   );
 }
-
-// ─── Composition source helpers ───────────────────────────────────────────────
-
-export { findClosestByAttribute, getPreferredClassSelector, getSourceFileForElement };