Enable TCH rules: Enforce correct TYPE_CHECKING usage

[HyeockJinKim]

Rules

TCH category includes:

• TCH001: Move import into TYPE_CHECKING block (used only for annotations)
• TCH002: Move import out of TYPE_CHECKING block (needed at runtime)
• TCH003: Move stdlib import into TYPE_CHECKING block

Purpose

Ensure correct usage of TYPE_CHECKING blocks:

1. Imports only used for type annotations should be in TYPE_CHECKING
2. Imports needed at runtime should NOT be in TYPE_CHECKING
3. Properly separates annotation-only imports from runtime imports

Benefits

• Faster import times (annotation-only imports not loaded at runtime)
• Accurate transitive dependency detection in lint/check/test
• Prevents runtime errors from imports that should be in TYPE_CHECKING
• Catches runtime-evaluated values incorrectly placed in TYPE_CHECKING

Auto-fix

✅ Available

Notes

• Critical for correct pants --changed-dependents=transitive behavior
• Helps with circular import prevention

JIRA Issue: BA-4023