feat!: lazy usearch initialization (v0.1.0 BREAKING)

[27Bslash6]

Summary

BREAKING CHANGE: usearch_fix() no longer runs automatically on import.

This PR removes the subprocess call that runs on every import litesearch, making imports clean and side-effect free.

Why This Matters

The current behavior runs install_name_tool (macOS) on every import, which:

• Breaks multiprocessing contexts (subprocess on fork)
• Fails in restricted environments (containers, CI)
• Surprises users with system modifications on innocent imports
• Prevents using litesearch without usearch installed

Migration

# Old (v0.0.x) - implicit, runs on import
import litesearch  # usearch_fix() ran here

# New (v0.1.0) - Option 1: automatic on first use (recommended)
db = setup_db('mydb.db', sem_search=True)  # fix applied here

# New (v0.1.0) - Option 2: explicit call if needed
import litesearch
litesearch.usearch_fix()  # call manually before setup_db

Changes

• Remove usearch_fix() call from __init__.py
• Keep usearch_fix importable for explicit use
• Add 4 import safety tests
• Version bump to 0.1.0

Dependencies

• Depends on fix: bug fixes, error handling, and test infrastructure (v0.0.6) #9 (bug fixes) being merged first
• The lazy init in setup_db() and idempotent flag in usearch_fix() from fix: bug fixes, error handling, and test infrastructure (v0.0.6) #9 make this safe

Test Plan

• 20 tests pass (16 from fix: bug fixes, error handling, and test infrastructure (v0.0.6) #9 + 4 new import safety tests)
• test_import_does_not_run_subprocess verifies no side effects
• setup_db(sem_search=False) works without usearch
• setup_db(sem_search=True) still loads usearch correctly