Remove the web helper; make install-and-use the product target

[veil-chow-fyaic]

User-requested removal

• Delete all four web helper source files, both browser/generator test files, and the Pages deployment workflow.
• Remove live website links from both README languages and guides; mark retained screenshot/case evidence historical and link recoverable pre-removal source.
• Make installation, explicit task choice and normal local-agent work the first-use acceptance; manual prompts and CLI samples do not satisfy existing-desktop installation.

Verification

• npm test: 460 pass, one optional native skip, zero failures; 55 schema and 7 transition cases pass; 149 Markdown files lint clean.
• The 14 removed tests belong only to the removed web helper. Core native skill, SDK, coordinator, CLI and historical agent evidence are retained.
• No remaining live Pages links or web imports in current source/docs. Historical source remains recoverable through Git.

After merge, disable this repository Pages site and verify the old endpoint is no longer served. No plugin-installation or independent-user success is claimed.