fix(results): encode download filenames

[bm1016bm-svg]

Summary

Encode the output filename as a single URL path segment before rendering preview and download links. This prevents # from starting a fragment and also handles other reserved characters without changing the trusted user/job path segments.

Validation

• bun test: 100 passed, 8 skipped
• Added 2 regression tests for reserved characters and Unicode filenames
• bun run lint:tsc
• bun run lint:knip
• bun run build
• Changed files pass Prettier

Closes #578

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Summary by cubic

Encode download filenames as a single URL path segment so preview and download links work with #, spaces, and Unicode. Path segments (e.g., user/job) remain unchanged.

• Bug Fixes
  • Added buildDownloadUrl helper to encode only the filename.
  • Updated results page to use the helper for preview and download links.
  • Added tests for reserved characters and Unicode filenames.

^{Written for commit b9495de. Summary will update on new commits.}

[C4illin]

Nice fix!

[cubic-dev-ai]

No issues found across 3 files

_{Re-trigger cubic}