refactor: complete OwlSQL v1 architecture hardening in M7

[tiagolauer]

Summary

• remove the Legacy compiler and redundant whole-query scanners
• finalize the modular monorepo, public API surface, architecture fitness functions, and release gates
• separate schema contracts from compiler internals and share parsed statements across public inference
• remove runtime SQL parsing from the SQLite adapter
• resolve the PostCSS and nanoid development-toolchain advisories

Verification

• core: 225 passed
• TypeScript plugin: 173 passed
• TypeScript 5.4, 5.6, 6, and 7 compatibility gates passed
• Node.js 20, 22, and 24 gates passed
• PostgreSQL, MySQL, and SQL Server integration suite: 36 passed
• package smoke and architecture fitness checks passed
• type budget: 134,857 instantiations against the 150,000 ceiling; Next delta +22 (+0.04%)
• npm audit: 0 vulnerabilities

Stack

Depends on #363. This is the final PR in the OwlSQL v1 architecture migration stack.