feat: deparse modified AST and improve INSERT pretty-printing

[pyramation]

Summary

This PR enables AST-based transformations for SQL statements inside PL/pgSQL function bodies and improves pretty-printing for INSERT statements.

plpgsql-deparser changes:

• For sql-stmt kind: Now uses Deparser.deparse() to convert the modified AST back to SQL
• For sql-expr kind: Still returns original string (backward compatible)
• For assign kind: Uses target and value strings directly (backward compatible)
• Added DehydrationOptions interface to thread SQL deparse options through

pgsql-deparser changes:

• VALUES tuple items: Put each value on its own line when isPretty()
• ON CONFLICT DO UPDATE SET: Put each assignment on its own line when isPretty()

Use case: Schema renaming in introspection exports - when SQL statements inside function bodies need their schema references transformed.

DehydrationOptions API

export interface DehydrationOptions {
  sqlDeparseOptions?: DeparserOptions;  // { pretty?: boolean, newline?, tab? }
}

// Usage:
dehydratePlpgsqlAst(ast, { sqlDeparseOptions: { pretty: true } });

This threads options through dehydratePlpgsqlAst → dehydrateNode → dehydrateQuery → Deparser.deparse().

Updates since last revision

• Rebuilt deparser and regenerated snapshot - INSERT VALUES and ON CONFLICT now properly pretty-print with each item on its own line
• Snapshot confirms the fix is working

Review & Testing Checklist for Human

• Verify formatting is acceptable: The deparsed output uses lowercase excluded (not EXCLUDED) and no column alignment in SET clauses - verify this is acceptable for your use case
• Check for formatting regressions: The snapshot shows different formatting (whitespace, AS aliases, parentheses placement) compared to original SQL - review the snapshot diff carefully
• Test schema renaming end-to-end: Run the schema renaming transform on actual exported SQL to verify schema references inside PL/pgSQL bodies are properly renamed

Recommended test plan:

1. Run pnpm test in packages/plpgsql-deparser - all 23 tests should pass
2. Run pnpm test in packages/deparser - verify no new failures
3. Test the transform script in constructive-db to verify schema renaming works end-to-end

Notes

• The sql-expr kind intentionally still returns original for backward compatibility
• Deparse failures fall back to returning the original string (safe default)
• DehydrationOptions is exported from the package for callers to use
• The pretty-printing produces multi-line output but does NOT preserve original stylistic choices (alignment, casing)

Link to Devin run: https://app.devin.ai/sessions/cf99eca9a417440f98c23cd9db41555b
Requested by: Dan Lynch (@pyramation)

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