docs: fix metric drift in canonical documentation

[google-labs-jules]

Updates metrics (extractors from 20 to 22, tests from 285 to 324, sink classes from 16 to 17, and proof score from 10/10 to 8/10) in README.md, AGENTS.md, ARCHITECTURE.md, and TEST-SPEC.md based on actual values. Confirmed that CHANGELOG.md is up to date with v0.10.0 changes.

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PR created automatically by Jules for task 4039504855622018015 started by @raccioly

[google-labs-jules]

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