refactor: drop unused exports detected by fallow auto-fix

Run `fallow fix --auto-fixable` to remove `export` keywords from symbols
fallow's reachability analysis identifies as unused. Keeps only the cases
where the symbol is still referenced internally in its own file (so
removing `export` doesn't surface a new oxlint `no-unused-vars` error).

Result: fallow dead-code findings drop from 276 → 208 (68 fewer unused
exports), with no behavior change — each symbol is still defined and used
exactly the same way within its file.

Reverted ~20 files where fallow's auto-fix would have created cascading
"declared but never used" lint errors — those are cases where the symbol
isn't used at all, and properly cleaning them up means deleting the
declaration, not just dropping `export`. Better to land that as a
separate, narrower PR rather than mixing it into a mechanical de-export.

Also reverted four false positives where fallow missed real consumers:
- `captureCost.ts` (renderOrchestrator has two separate import blocks
  from the same module; fallow only saw the first)
- `propertyPanelHelpers.ts`, `domEditingLayers.ts` (real internal uses
  fallow's reachability missed)
- `render.ts` (functions imported via `await import()` dynamic import,
  which fallow's static analysis doesn't follow)

Test plan: bun run --filter '*' typecheck (clean), oxlint + oxfmt clean,
cli/core/studio/engine vitest suites pass (335 + 917 + 576 + 605 tests).

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

@@ -1,7 +1,7 @@
 import { useState, useRef, useEffect, type ReactNode } from "react";
 import { Zap } from "../../icons/SystemIcons";
 
-export const FIELD =
+const FIELD =
   "min-w-0 rounded-xl border border-neutral-800 bg-neutral-900/95 px-3 py-2 text-neutral-100 shadow-[inset_0_1px_0_rgba(255,255,255,0.03)] transition-colors focus-within:border-neutral-600";
 export const LABEL = "text-[11px] font-medium uppercase tracking-[0.18em] text-neutral-500";
 export const RESPONSIVE_GRID = "grid grid-cols-[repeat(auto-fit,minmax(118px,1fr))] gap-3";
@@ -30,7 +30,7 @@ export function parsePlainNumber(value: string): number | null {
 
 // ── CommitField ──
 
-export function CommitField({
+function CommitField({
   value,
   disabled,
   onCommit,

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

@@ -10,7 +10,7 @@ import type { GroupOverlayItem } from "./domEditOverlayGeometry";
 export type GestureKind = "drag" | "resize" | "rotate";
 
 export const BLOCKED_MOVE_THRESHOLD_PX = 4;
-export const MIN_RESIZE_EDGE_PX = 20;
+const MIN_RESIZE_EDGE_PX = 20;
 const ROTATION_COMMIT_EPSILON_DEGREES = 0.05;
 const ROTATION_SNAP_DEGREES = 15;
 

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

@@ -163,7 +163,7 @@ export function normalizeTimelineCompositionSource(value: string | undefined): s
 
 // ─── CSS escaping ─────────────────────────────────────────────────────────────
 
-export function escapeCssIdentifier(value: string): string {
+function escapeCssIdentifier(value: string): string {
   const css = globalThis.CSS as { escape?: (input: string) => string } | undefined;
   if (typeof css?.escape === "function") return css.escape(value);
 

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

@@ -8,7 +8,7 @@ const FONT_EXT_RE = /\.(eot|otf|ttc|ttf|woff2?)$/i;
 const FONT_STYLE_SUFFIX_RE =
   /\s+(thin|extralight|extra light|light|regular|roman|medium|semibold|semi bold|bold|extrabold|extra bold|black|italic|oblique|variable)$/i;
 
-export function cssString(value: string): string {
+function cssString(value: string): string {
   return JSON.stringify(value);
 }
 

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

@@ -370,7 +370,7 @@ function formatHex(channel: number): string {
   return channel.toString(16).padStart(2, "0");
 }
 
-export function interpolateGradientStopColor(model: GradientModel, position: number): string {
+function interpolateGradientStopColor(model: GradientModel, position: number): string {
   const clampedPosition = clamp(position, 0, 100);
   const sortedStops = [...model.stops].sort((a, b) => a.position - b.position);
   const exact = sortedStops.find((stop) => Math.abs(stop.position - clampedPosition) < 0.001);

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

@@ -256,7 +256,7 @@ export function createManualOffsetDragMember(input: {
   };
 }
 
-export function resolveManualOffsetDragMemberOffset(
+function resolveManualOffsetDragMemberOffset(
   member: ManualOffsetDragMember,
   dx: number,
   dy: number,
@@ -289,7 +289,7 @@ export function applyManualOffsetDragCommit(
   return offset;
 }
 
-export function restoreManualOffsetDragMember(member: ManualOffsetDragMember): void {
+function restoreManualOffsetDragMember(member: ManualOffsetDragMember): void {
   restoreStudioPathOffset(member.element, member.initialPathOffset);
   endStudioManualEditGesture(member.element, member.gestureToken);
 }

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

@@ -18,7 +18,7 @@ const COLOR_PICKER_SIZE = { width: 292, height: 386 };
 /*  ColorSlider                                                        */
 /* ------------------------------------------------------------------ */
 
-export function ColorSlider({
+function ColorSlider({
   label,
   value,
   min,

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

@@ -1,7 +1,7 @@
 import { useCallback, useEffect, useRef, useState, type ReactNode } from "react";
 import { adjustNumericToken, FIELD, LABEL, parseNumericToken } from "./propertyPanelHelpers";
 
-export function CommitField({
+function CommitField({
   value,
   disabled,
   liveCommit,

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

@@ -129,7 +129,7 @@ export function buildStudioGsapPresetMotion(
 
 // ── Manifest parse/serialize ──
 
-export function parseMotionValues(value: unknown): StudioGsapMotionValues | null {
+function parseMotionValues(value: unknown): StudioGsapMotionValues | null {
   if (!value || typeof value !== "object") return null;
   const record = value as Record<string, unknown>;
   const parsed: StudioGsapMotionValues = {};