chore!: remove main fn from generated code

[nyurik]

there is no need to generate fn main, unless we are doing testing. The main fn is now added to the snapshot at the end, but is no longer part of the generator.

Additionally, move could not generate Rust code error context to the top level for consistency.

[Copilot]

Pull request overview

This PR removes the fn main() function from the code generator output, instead appending it only in test snapshots where trybuild requires a main function. It also moves the "could not generate Rust code" error context from an intermediate level to the top-level generate() method for consistency.

Changes:

• Extracted a create_content helper function in tests that appends fn main() to generated code for trybuild compatibility
• Removed main function generation from src/lib.rs code generator
• Moved error context addition from codegen() to generate() for consistency
• Updated all test snapshots to reflect the new main function placement (at end instead of middle)

Reviewed changes

Copilot reviewed 82 out of 82 changed files in this pull request and generated 1 comment.

File	Description
tests/snapshots.rs	Refactored to extract create_content() helper that appends main function for testing; both test functions now use this helper
src/lib.rs	Removed main function generation from codegen() and moved error context to generate() for consistency
tests-snapshots/*.snap.rs (85 files)	Updated snapshots showing main function moved from middle to end of generated code

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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