fix(core): normalize Act cache URL keys

[RitwijParmar]

Fixes #2189.

This changes ActCache key derivation so query parameter order no longer causes silent cache misses. The raw page URL is still stored in the cache entry for debugging. Only the hash input is normalized.

I also added a legacy raw URL key fallback. That keeps existing cache files reachable after the normalized key starts being used, instead of making old entries quietly unreachable.

What changed

• Added normalizeUrlForCacheKey for conservative query parameter sorting.
• Used the normalized URL when building Act cache keys.
• Preserved the raw pageUrl in ActCacheContext and stored cache entries.
• Added legacyCacheKey fallback reads for old raw URL cache files.
• Added tests for reordered query params, stable URLs, malformed inputs, repeated params, and legacy fallback replay.

Validation

• bunx prettier --check on changed files passed.
• git diff --check passed.
• Direct Bun runtime check for normalizeUrlForCacheKey passed.

Could not run the full Vitest path locally because pnpm is not installed in this checkout, and bunx vitest fails before running tests due a Rolldown native binding code signature error on macOS. Bundling ActCache directly also hits Stagehand's generated version file, so I left the full suite to CI.

---

Summary by cubic

Normalize Act cache keys by sorting URL query parameters so reordering no longer causes cache misses. Adds a legacy raw-URL fallback to keep existing cache entries accessible (fixes #2189).

• Bug Fixes
  • Use a normalized URL only for cache key hashing; keep the raw pageUrl in context and stored entries.
  • Fallback to legacy raw-URL keys when normalized reads miss, preserving access to old cache files.
  • Add tests for param reordering, repeated params, malformed inputs, stable URLs, and legacy fallback.

^{Written for commit bee1a21. Summary will update on new commits.}

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