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/core/src/parsers/htmlParser.ts

@@ -10,7 +10,6 @@ import type {
   StageZoomKeyframe,
   CompositionVariable,
 } from "../core.types";
-import { CANVAS_DIMENSIONS } from "../core.types";
 import {
   parseGsapScript,
   validateCompositionGsap,
@@ -902,5 +901,3 @@ function extractGsapScript(doc: Document): string | null {
   }
   return null;
 }
-
-export { CANVAS_DIMENSIONS };