Release 0.3.0: complete product and numerical documentation

[terrizoaguimor]

Summary

• rewrite the root README around the exact 0.3.0 support matrix, release installation, source onboarding, CLI/C ABI/HTTP/gateway capabilities, hardware profiles, evidence, packaging, and explicit non-claims
• replace the numerical overview with a complete I2_S/I8_S contract: packing, scales, activation quantization, unsigned correction, zero-row recovery, FFN graph, shape bounds, validator limits, and evidence scope
• document Ubuntu 24.04 as the official Linux release build environment without overclaiming older-userspace portability
• pin the certified Hugging Face source revision by default, record both C and C++ compiler versions in release manifests, clarify historical CPU/GPU notes, and make the model release job conditional on configured fixtures

Validation

• Python conversion/logits/wrapper tests pass
• Rust format/check/Clippy/tests pass, including native Hyphae E2E
• CMake product build succeeds
• shell/Python syntax and diff checks pass

Release

After merge, the final v0.3.0 tag and all six Linux archive/manifest assets will be produced from a clean Ubuntu 24.04 checkout.