Fix IDE static analysis diagnostics and type checking errors

[DevAbdullah90]

Description

Currently, there are several Pyright/Pyrefly static analysis errors and diagnostics across the Google Antigravity Python SDK workspace. This issue tracks the fixes for these problems.

We have fixed these errors on the fork branch fix-ide-type-diagnostics. Since direct pull requests to this repository are restricted to collaborators only, we would appreciate it if you could review the changes or invite us as a collaborator to submit a Pull Request.

Proposed Changes

The changes include:

1. Core SDK Types (google/antigravity/types.py):
   • Imported cast and casted return values and validation error dictionaries to prevent invariant list type errors.
   • Handled IsADirectoryError check in file reading.
2. Local Connection (google/antigravity/connections/local/local_connection.py):
   • Removed redundant class-level target attribute to resolve conflicts with parent class fields.
   • Defined _TARGET_MAP to resolve type lookups, and properly typed local connection strategy variables.
   • Updated connection send method signature with **kwargs to match parent interface.
3. Local Connection Tests (google/antigravity/connections/local/local_connection_test.py):
   • Added explicit metadata imports and assertions to guarantee non-null thread and configuration variables.
4. Workspace Configurations:
   • Added pyrightconfig.json and pytest configurations (conftest.py) to manage local test run contexts cleanly.

Link to fork branch with full implementation: https://github.com/DevAbdullah90/antigravity-sdk-python/tree/fix-ide-type-diagnostics