Open Agent SDK Rust v0.11.3

This patch fixes client lifecycle and tool-history bugs while preserving public signatures and defaults.

• Clear stale output when starting a request or clearing history, close failed streams, and honor cancellation during automatic tool rounds.
• Preserve manual tool-result call IDs in both OpenAI and Anthropic requests.
• Keep repository-only package checks out of the crate so unpacked sources can run their tests.
• Handle UTF-8 image URLs safely in logs and reject non-ASCII Base64 input.
• Count serialized tool JSON without temporary allocations; the four tool-token estimation benchmarks improved by 50–53% on GitHub's Linux runner.
• Remove redundant tests, unused dependencies, and repeated documentation while retaining coverage of observable behavior.
• Scope routine mutation checks to the affected tests, with full sweeps for integration changes, manual dispatch, and the monthly schedule.

See the changelog for details.