Clean up redundant Python codegen lambdas

[stephentoub]

This copies the Python generator cleanup from #1103 into this branch. It removes redundant passthrough lambdas from generated Python so the output is cleaner and avoids unnecessary-lambda static analysis noise without changing behavior.

What changed

• add a post-processing pass in scripts/codegen/python.ts that rewrites lambda x: callable(x) to the direct callable when it is safe to do so
• update the Python codegen test to expect the simplified form and add a regression test for string, list, and nested dataclass callables
• regenerate python/copilot/generated/session_events.py so the checked-in generated output matches the new generator

Notes

• this is a generator/output cleanup only; it does not change the protocol schema or runtime behavior
• python/copilot/generated/rpc.py did not change with the current schema

[Copilot]

Pull request overview

This PR cleans up Python code generation output by removing redundant passthrough lambdas (e.g., lambda x: from_str(x) → from_str) to reduce noise in generated code and avoid static analysis “unnecessary lambda” findings, without changing the intended parsing/serialization behavior.

Changes:

• Added a Python codegen post-processing pass (unwrapRedundantPythonLambdas) to collapse lambda x: callable(x) into callable when safe.
• Updated/extended the Node-based Python codegen tests to assert the simplified output and cover string/list/nested-dataclass callables.
• Regenerated python/copilot/generated/session_events.py to reflect the new generator output.

Show a summary per file

File	Description
scripts/codegen/python.ts	Adds the lambda-unwrapping post-process and applies it to session-events and RPC generation output.
python/copilot/generated/session_events.py	Regenerated output showing collapsed redundant lambdas throughout the generated dataclass converters.
nodejs/test/python-codegen.test.ts	Updates an existing expectation and adds a regression test validating the lambda unwrapping behavior.

Copilot's findings

• Files reviewed: 2/3 changed files
• Comments generated: 0