feat(uv): add uv run filtering to prevent incorrect run injection (fixes #2841)

[jlaportebot]

Summary

Adds support for uv run command filtering to prevent incorrect routing through rtk run when users invoke uv run <tool>. This addresses issue #2841 where uv run (high-frequency Python command) was unhandled.

Changes

• New filter module: src/cmds/python/uv_cmd.rs - Handles uv sync, uv pip list/outdated, and uv run <tool> with routing to appropriate filters
• Discovery rule: Added pattern for ^uv\s+run\s+ in src/discover/rules.rs with 70% savings estimate
• CLI integration: Added Uv variant to Commands enum in src/main.rs with proper routing
• Meta-command registration: Added "uv" to RTK_META_COMMANDS to prevent fallback

Quality Checks

All quality gates pass locally:

• cargo check ✓
• cargo test ✓ (2242+ tests pass)
• cargo clippy --all-targets ✓ (zero warnings)
• cargo fmt --all --check ✓

Testing

# Test uv sync filtering
rtk uv sync

# Test uv pip list
rtk uv pip list --format=json

# Test uv run routing to pytest
rtk uv run pytest tests/

# Test uv run routing to ruff
rtk uv run ruff check .

# Test uv run routing to mypy
rtk uv run mypy src/

# Test uv run passthrough for unknown tools
rtk uv run some-unknown-tool

Fixes #2841