[kvlonge]

Why

M3g chunk 2 moves the remaining Python attachment work for SQL tests, scenarios and functions onto the native path behind the native-preview engine. Output stays byte-identical to Python or defers to it.

Changes

All under the preview ATTACHMENTS stage:

• SQL test @param("name") references are scanned natively (quotes, comments, dollar quotes, Python whitespace). Python still renders the typed values; malformed or undeclared references defer.
• The omitted trailing SELECT 1 of test and scenario bodies is located natively under each adapter's lexical syntax. Non-ASCII keyword text defers.
• The raw pass for macro, UDF and table-function tests stays Python on every engine (aligning extractors is M3j).
• Scenario CTEs are extracted and classified natively. Dialect-sensitive SQL, quoted or non-ASCII CTE names, case-mapped characters and every error defer to Python.
• Model test targets (mocks, macro mocks, expected models, assertion targets) and scenario source references are validated natively with Python's messages, against one catalog built per compile.
• SQL and Python function headers (arguments, returns, table columns, tags, description, runtime, entry point, packages) are parsed natively, and function namespaces resolve natively. Template expansion keeps Python's order and labels.
• fix(test): rewrite references in helper CTEs and order them after their dependencies #1019's helper CTE checks (reachability, P013) stay in Python and run after the native target validation, as before.

Verification

• cargo test --workspace (201), clippy and fmt (1.98.0)
• Seeded Python-vs-preview parity tests for each part, plus the whole-project test with parameterized, macro-mode, omitted-SELECT, raw direct-logic regression and fix(test): rewrite references in helper CTEs and order them after their dependencies #1019 helper CTE tests (helper __ref, helper chains, unread helpers, P013)
• make compiler-differential with CI's coverage flags: 216/216; make compiler-differential-shipped: 210/210
• tests/e2e/scripts/compiler_differential: 24 passed
• make check-ci, make test (11795 passed), hygiene scan