chore(ci): make bundle budget resilient to runtime chunk changes

[ClodoCapeo]

Problem

Solar's bundle-size gate required runtime-owned chunk prefixes (index, tree, broadcast, control, test, status-pill). A runtime minor rename or merge could fail CI even when the emitted ESM graph and budgets were valid.

Change

• derive the library bundles from the emitted ESM import graph rooted at dist/solar.js;
• identify mode entries from the stable BroadcastMode / ControlMode / TestMode loader exports, not emitted filenames;
• count each reachable emitted file once per mode, including merged runtime chunks;
• retain per-mode gzip budgets and the host budget;
• retain a graph-based broadcast -> distinct overlay-entry guard;
• add a Node regression test with renamed chunks and a control/test merged chunk;
• run the regression test as part of npm test.

Evidence

• npm run lint — passed
• npm run typecheck — passed
• npm test — 112 Vitest tests + 2 bundle-graph tests passed
• npm run build — passed
• npm run check:bundle — passed
  • broadcast: 41,254 B gz
  • control: 43,247 B gz
  • test: 44,813 B gz
  • host: 143,201 B gz
• signed commit: dfe282cbad92508af872bba679d34d2ecfa48a4f

npm run test:e2e was attempted but could not launch because this workstation lacks the Playwright Chromium and Headless Shell executables; the CDN install did not complete. No application assertion ran or failed.

Refs #5