feat: add install timeout option

[KimHyeongRae0]

Summary

• add agent-browser install --timeout/-t <seconds> with the existing 120 second default
• pass the configured timeout to Chrome for Testing metadata and binary download HTTP requests
• keep --with-deps behavior unchanged
• update CLI help, README, docs, and core skill references

Fixes #1285.

Testing

• cargo fmt --manifest-path cli/Cargo.toml -- --check
• git diff --check
• CARGO_INCREMENTAL=0 cargo test --manifest-path cli/Cargo.toml --profile ci install::tests -- --test-threads=1

[vercel]

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