docs: publish M2 current-main status

[Legender134]

Summary

• publish the current-main General Counterfactual M2 compatibility status in both READMEs
• document the advanced planar_translate@2 API and concepts boundary
• preserve the stable generation API and exact v0.1.1 quickstart; no v0.2.0 release

Snapshot provenance

• development merge: a2d4c96e854e644348555d962e7a28fbc5813178
• verified public snapshot tree SHA-256: ce1ed0e25d507b2fd4debc0585e437d7b6134ba01243bcd996de00ea4d024eb5
• candidate is byte-identical to the complete 150-file snapshot
• exact diff: README.md, README_EN.md, docs/api.md, docs/concepts.md

Verification

• public smoke: 39 passed
• wheel and sdist build succeeded
• git diff --check passed

Boundaries

• no source, dependency, generation, or release-tag changes
• no Unity, AI2-THOR controller, native generation, GPU, or M3 implementation