feat(rust): add send_typing_with_status

[KyleYe]

Summary

• Add WeChatBot::send_typing_with_status(user_id, status) to the Rust SDK.
• Preserve the existing send_typing(user_id) behavior by delegating to status 1.
• Document status 1 as start and status 2 as stop.
• Add a public API regression test covering both the existing and new method signatures.

Motivation

The iLink /sendtyping endpoint supports status 1 and 2, and the low-level Rust ILinkClient::send_typing method already accepts a status parameter. However, the high-level WeChatBot::send_typing method hardcodes status 1, so Rust callers cannot explicitly stop the typing indicator through the high-level API.

Developer impact

Existing calls remain unchanged:

bot.send_typing(user_id).await?;

Callers can now explicitly stop the indicator:

bot.send_typing_with_status(user_id, 2).await?;

Backward compatibility

No existing public method signatures are changed. Existing calls to send_typing(user_id) retain their current status-1 behavior.

Test plan

• cargo fmt --all -- --check
• cargo build
• cargo test (49 unit tests, 1 public API integration test, and 2 doc tests)
• git diff --check upstream/main...HEAD

Supersedes #100, which was closed to resubmit this change from a fresh branch.