Polyfills cleanup

[rymsha]

Fixes #2253

XP 8 runs on GraalVM 25, which lets us drop most of the hand-rolled SSR polyfills:

• TextEncoder: GraalJS provides native TextEncoder/TextDecoder via the js.text-encoding option (stable in GraalJS 25, default off). It is now enabled in EngineFactory, and the @sinonjs/text-encoding polyfill and dependency are removed. Bonus: SSR contexts also get a native TextDecoder, which the old polyfill never provided.
• console: GraalJS provides a native console by default (js.console, stable, default on) with a fuller method set (log, debug, info, warn, error, assert, time, group, …) than the old print-based mapping — the shim in polyfillBasics.js was dead code.
• polyfillBasics.js: with the console shim gone, only the minimal process shim remained — moved into nodePolyfills.ts and the file is deleted, so every SSR context loads one asset less.
• timers: the ~70-line timers.ts (branded types, exported no-op functions, @ts-expect-error suppressions) is replaced with inline one-line ??= no-op shims in nodePolyfills.ts. Behavior preserved: setTimeout/setInterval still return 0, existing globals are never overwritten.
• Also removed the now-unused @rollup/plugin-alias dependency and its stale @sinonjs/text-encoding alias from rollup.config.nodePolyfills.mjs.

Verification

• ./gradlew test passes, including RendererTest.render_real_react_component_via_server_edge, which renders real React 19 through react-dom/server.edge against the production-compiled polyfill bundle — server.edge looks up TextEncoder at module-load time, so this exercises the native GraalJS implementation.
• Jest (11/11), rollup polyfill build, and check:types:graal all pass.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 22.85%. Comparing base (aef55db) to head (275030f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2254   +/-   ##
=======================================
  Coverage   22.85%   22.85%           
=======================================
  Files           1        1           
  Lines          35       35           
=======================================
  Hits            8        8           
  Misses         27       27           

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