Bundle Keito agent skill with CLI

[sionsmith]

Summary

• Bundle the Keito time-tracking skill inside keito-cli and make keito skill install default to the bundled source.
• Add a gstack-style ./setup entrypoint plus keito skill team-init optional|required for repo-level agent onboarding.
• Document Keito positioning as billing and profitability infrastructure for AI-native services companies.
• Include the existing calendar and desktop time-entry source support in the 0.1.7 release notes.

Release

• Bumps keito-cli from 0.1.6 to 0.1.7.
• After merge to main, release-tagger.yml should create v0.1.7 and dispatch release.yml.
• Do not manually tag unless the automated tagger fails.

Validation

• cargo fmt --all -- --check
• cargo clippy --all-targets -- -D warnings
• cargo test --all-targets
• cargo build --release
• ./target/release/keito --version
• ./target/release/keito --help
• cargo run --bin gen-man -- /tmp/keito-man
• python3 .github/scripts/check-release-version.py --base-ref origin/main --mode guard --event-name pull_request
• cargo audit (passes with the repo-allowed unmaintained proc-macro-error2 warning via tabled)