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/cli/src/browser/manager.ts

@@ -13,12 +13,6 @@ const CACHE_DIR = join(homedir(), ".cache", "hyperframes", "chrome");
 // too or it silently picks system Chrome over a perfectly good headless-shell.
 const PUPPETEER_CACHE_DIR = join(homedir(), ".cache", "puppeteer", "chrome-headless-shell");
 
-/** Override browser path via --browser-path flag. Takes priority over env var. */
-let _browserPathOverride: string | undefined;
-export function setBrowserPath(path: string): void {
-  _browserPathOverride = path;
-}
-
 export type BrowserSource = "env" | "cache" | "system" | "download";
 
 export interface BrowserResult {
@@ -61,10 +55,6 @@ function whichBinary(name: string): string | undefined {
 }
 
 function findFromEnv(): BrowserResult | undefined {
-  // --browser-path flag takes priority
-  if (_browserPathOverride && existsSync(_browserPathOverride)) {
-    return { executablePath: _browserPathOverride, source: "env" };
-  }
   const envPath = process.env["HYPERFRAMES_BROWSER_PATH"];
   if (envPath && existsSync(envPath)) {
     return { executablePath: envPath, source: "env" };