Add c, cpp, and java to the highlight.js language bundle for code block
rendering. These are among the most commonly used languages in AI coding
conversations and were previously unsupported, falling back to plain text.
Also adds aliases: h (C headers), cc/cxx/c++/hpp/hxx (C++ variants).
- Set up Vitest with 27 tests across 3 test suites
- relativeTime: edge cases, time buckets, future timestamps
- sessionDisplayName: labels, kinds, channels, UUID truncation
- messagesToMarkdown: roles, blocks, tool calls, system events
- Add test and test:watch npm scripts
- Add test step to CI workflow