chore: version pylance 9.0.1+exa.4

[jan-exa]

Summary

Release version bump for the exa fork: pylance 9.0.1+exa.3 → 9.0.1+exa.4 (python/Cargo.toml + python/Cargo.lock), picking up #18 (empty/null blanks in add_blanks — fixes the offset overflow on heavily-deleted fragments). Same two-line pattern as #15. Tag v9.0.1-exa.4 follows the merge to trigger wheel builds.

Link to Devin session: https://app.devin.ai/sessions/7cd5f358690a4d7cb4fbe13d6b5e4ad5
Requested by: @jan-exa

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring