feat: Antigravity IDE native host support with 800-line pagination limit safety

[nicezic]

This PR introduces robust, native support for Google DeepMind's Antigravity IDE, closing the loop on previous attempts like #413 and extending the great work in #894.

Key Contributions:

1. Explicit Tool Dialect Translation: Translates general instructions like 'use the Bash tool' directly into Antigravity's specific dialect ('use the run_command tool'), 'Agent tool' to 'browser_subagent', preventing hallucinated tool calls.
2. First-in-class Pagination Safety: Antigravity has a hard limit truncating view_file at 800 lines, documented by users in feat: add Antigravity / Gemini CLI as supported host #413, which silently breaks mammoth skills like /office-hours. This PR modifies the compiler core (gen-skill-docs.ts) with a paginationWarningLimit property. When generated documentation exceeds this limit, it injects a highly visible Markdown caution block forcing the AI agent to paginate.

Generated and verified with bun run gen:skill-docs --host antigravity.
Co-Authored-By: Antigravity IDE

[doogiehowzer]

Many thanks!