[kvlonge]

Why

Phase 1 of the Rust-hosted SQLBuild port (CHI-589): continue moving compiler stages into the native extension and deleting the Python they replace.

Changes

• Native compiler frontier and stage captures (encoder, writer and capture sequence deleted from Python).
• Native target validation (S101–S104) and target defaults inside the compile driver.
• Native macro store keys and module digests, model deferral inputs, relation targets, diff selection and Python plan entries; the related pipeline helpers and wrappers are deleted.
• compile/_helpers/assembly package deleted: semantic shapes, coverage, source bindings, hand-built models, binding positions and metadata validation are native; so are SemanticCompletionInputs and PythonModelAnalysis.
• Macro analysis walks the shared CPython tree; the duplicate reconstruction is removed.
• Movable Python: 125,499 → 122,079 lines.

Intentional differences: native encoders stop at a nesting depth of 900; a native panic while saving the macro store now propagates instead of being logged.

Verification

• Compiler differential: 371 projects as expected, goldens unchanged.
• Byte-identical compile output (cold and one-model edit) against the previous main on a generated 1k-model project and a large private project.
• 6,145 focused compiler, CLI, rule-engine and integration tests; make check-ci; public-repository hygiene scan.
• Independent review of the combined diff: no findings.