Clarify standalone project identity

[Tom-R-Main]

Summary

• describe pdf-parser as an independent project while retaining the exact upstream source, imported commit, and license attribution
• add a search description to the browser demo
• remove the outdated claim that the current WebAssembly artifact is approximately 90 KB

Verification

• Zig 0.16.0 confirmed
• zig fmt --check $(git ls-files '*.zig')
• zig build test --summary all — 2,886 tests passed
• zig build --summary all
• zig build wasm --summary all
• local HTTP smoke test returned 200 for the page and pdf_parser.wasm

Publication boundary

This PR does not rename the repository or add a canonical URL. Those changes remain behind the separate rename and GitHub Pages approval gate.

[greptile-apps]

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