refactor: migrate Dict and List to native types across codebase

[rashmiraghunandan]

Migrated from deprecated typing.Dict and typing.List to native dict and list types across the entire codebase as part of Python 3.9+ modernization effort (74 files total).

Changes

Type Migrations

• Updated all type annotations from typing.List/Dict to native list/dict
• Removed List and Dict imports from 70+ files
• Migrated test files to use native types

Core Fixes

• type_helpers.py: Removed legacy list: List normalization mapping, updated is_list() to use native list type
• type_evaluator.py: Fixed _is_acceptable_candidate() to extract origin types before issubclass() calls (subscripted generics like list[str] cannot be used with issubclass())
• type_evaluator.py: Updated _is_single_arg_invariant_generic() to check for native list instead of typing.List

Test Updates

• Updated 3 test expectation files (.txt) to reflect new error messages showing list[...] instead of List[...]
• Updated test files to use native types and removed unsupported type tests that are now supported
• Updated test_type_evaluator.py: Removed Union[list[str], str] and bare list from unsupported types (now supported with native types)

Migration Approach

1. Manually migrated 6 UI API files to establish pattern
2. Created automation script for systematic migration of remaining files
3. Fixed type system compatibility issues
4. Updated all test expectations

Files Changed (74 total)

• Engine modules: AST, validators, executors, stdlib, UDF system
• Worker lib: config, storage, discovery, instrumentation, pub/sub
• UI API: validators, views, lib modules
• Tests: unit tests and test expectation files

All type checking (mypy), linting (ruff), and integration tests pass.

Fixes #25