Release Python client v0.0.12

[terjekv]

Summary

• release the organization migration and current project metadata
• ship the validated client hot-path optimizations and lazy HTTPX transport initialization
• publish the refreshed dependency set and immutable GitHub Action pins
• declare compatibility with and test against Treetop REST v0.0.12

Compatibility

This is a backward-compatible patch release. The distribution remains named treetop-client, Python 3.12 remains the minimum, the HTTPX runtime constraint is unchanged, and the public synchronous and asynchronous APIs are preserved.

Verification

• pyright and basedpyright
• 54 unit tests
• 29 Compose-backed integration tests against REST v0.0.12
• v0.0.12 wheel and source distribution builds
• Markdown lint

[codspeed]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing release/v0.0.12 (822d86d) with main (6290fb6)}