fix(verso): publish item-style project readers

[imathwy]

Summary

• discover item-per-module book and paper layouts and generate compact Verso readers
• generate indexes for imports-only paper sections whose part modules contain the reading content
• reject semantically empty required Verso artifacts during release acceptance
• preserve bounded GitHub Pages output and full self-hosted output

Validation

• ./sdk/test.sh: 138 tests passed
• repository tests: 50 tests passed
• SiFlow SDK tests: 169 tests passed
• Ruff, Python compile, and git diff checks passed
• real v4.30 inventory: 91 readers and 5,980 item roots
• minimal real Verso compiles passed for May Chap01, TR_LALM items, and OnSome Section01

The release will reuse immutable Lean and API documentation caches; publication remains gated on local Pages and self-hosted artifact acceptance.