Release Tau 0.3.9 - #577

Release Tau 0.3.9

Prepares the v0.3.9 patch release.

Changes

• Bump tau-ai version to 0.3.9 in pyproject.toml and uv.lock
• Update the TUI sidebar brand test expectation
• Add structured 0.3.9 release notes

Highlights since v0.3.8

• Autocomplete dot-prefixed project paths and keep successful export destinations visible
• Add Kimi K3 to the Hugging Face catalog
• Honor model-specific output limits for Anthropic-protocol models
• Persist interrupted tool results and repair malformed history from older sessions
• Improve light-theme Markdown accents

Checks

• uv run mypy ✅
• uv run ruff check . ✅
• uv run ruff format --check . ✅
• uv run pytest ✅ (1467 passed, 2 skipped)
• Hugo documentation build and Pagefind indexing ✅