fix(validation): fix unreachable allow_override code in llm_validator

[Waqar53]

Fixes a critical bug where the allow_override feature in llm_validator() was completely broken - the code was unreachable dead code due to an assert statement.

The Bug

# Line 69 - Raises AssertionError if resp.is_valid is False
assert resp.is_valid, resp.reason
# Lines 71-73 - UNREACHABLE! (assert already crashed)
if allow_override and not resp.is_valid and resp.fixed_value is not None:
    return resp.fixed_value  # This line NEVER executes
Impact: Users who set allow_override=True expecting auto-correction get an AssertionError instead of the corrected value.

The Fix
python
if not resp.is_valid:
    if allow_override and resp.fixed_value is not None:
        return resp.fixed_value
    raise ValueError(resp.reason)
return v
Changes
✅ Restructure logic so 
allow_override
 check runs before any exception
✅ Use ValueError instead of assert for better error handling
✅ Update docstring to match actual parameters
✅ Add 5 comprehensive tests for 
allow_override
 functionality
Type of Change
 Bug fix (non-breaking change that fixes an issue)
Testing
Added 
tests/test_llm_validators.py
 with 5 tests covering:

Valid input returns unchanged
Invalid with allow_override=True returns 
fixed_value
Invalid with allow_override=False raises ValueError
Invalid without 
fixed_value
 raises ValueError
Default allow_override=False behavior