Remove stale search mode deprecation deadline - #130

Our Search warning says the old mode names stop working after June 2026, even though we still translate them to V1 modes. We want existing scripts to keep working while giving users accurate guidance on which names to use.

We replace the expired deadline with a warning that names the replacement mode. The mappings stay the same: fast and one-shot become basic, and agentic becomes advanced. We also list turbo, basic, and advanced first in help and label the old names as deprecated aliases.

Our tests now check the full warning text and cover turbo alongside the other native modes as a no-warning choice. They still check that aliases reach the SDK as V1 modes and that JSON output stays clean.

Validation

Recorded validation:

• uv run pytest tests/test_cli.py -k SearchDeprecationWarnings -q: 6 passed.
• uv run --frozen pytest tests/ -q: 778 passed.
• Ruff lint and formatting, Tach, and Ty checks: uv run --frozen ruff check parallel_web_tools/ tests/, uv run --frozen ruff format --check parallel_web_tools/ tests/, uv run --frozen tach check, and uv run --frozen ty check.