docs: fix generated rustdoc links

[wyf027]

Closes #297.

Summary

• update generated README Rustdoc links from api::Type to current docs.rs paths like api/struct.Type.html
• link common marker traits to google-apis-common/latest documentation
• refresh gen/sheets4/README.md so the reported Sheets API links resolve now

Verification

• git diff --check
• PYTHONPATH=src uv run --with mako --with inflect python - <<'PY' ... Template(filename='src/generator/templates/api/lib/lib.mako') ... PY
• checked 28 unique docs.rs links in gen/sheets4/README.md; all updated google-sheets4/google-apis-common links returned HTTP 200

Note: an existing yup-oauth2/*/trait.AuthenticatorDelegate.html link still 404s because current yup-oauth2 no longer exposes that trait; this PR stays focused on the generated Rustdoc links reported for the Sheets API README.

[Byron]

Thanks a lot.

I validated some of these newly generated links and they work, whereas the old ones don't.
Why it works a little bit puzzling to me still, and I'd like to see lib.rs regenerated as well as ${lib.docs(...) is called from there as well.

[wyf027]

Addressed the requested lib.rs regeneration in d3623ee.

What changed:

• Regenerated gen/sheets4/src/lib.rs so the hub references now use api::Sheets, matching the generator/template behavior already reflected in gen/sheets4/README.md.
• Left unrelated regenerated api.rs formatting noise out of the commit.

Validation:

• cargo check --manifest-path gen/sheets4/Cargo.toml passed.
• cargo doc --manifest-path gen/sheets4/Cargo.toml --no-deps passed; it still emits pre-existing generated API warnings for unrelated Sheets schema text links/bare URL.

[Byron]

Thanks a lot!

I still don't really understand how this works. To my mind that change should duplicate a line but apparently it doesn't. I also don't want to spend more time on it (and validate it locally), so let's just merge - in the worst case links in markdown files are more broken or docs don't build, something that CI might actually be doing as well.