feat: central logging via rich + stdlib (TASK 030)

[nceglia]

Summary

• Adds genevector/_logging.py with get_logger(name) and a shared rich Console.
• Replaces all bcolors + print() usage in data.py, model.py, and embedding.py with module-level loggers.
• Default level is INFO; override via GENEVECTOR_LOG_LEVEL env var (e.g. WARNING, ERROR).
• RichHandler on TTY, plain StreamHandler otherwise (CI logs, redirects, sandboxes).
• Foundation for TASKs 031-035 (panels, progress bars, verbose API, run summaries, unified progress).

Mapping

Old	New
bcolors.OK* / HEADER / BOLD + print()	logger.info()
bcolors.WARNING + print()	logger.warning()
bcolors.FAIL + print()	logger.error()
Plain print()	logger.info()

Decorative asterisk separators around "Loading Dataset." dropped — TASK 031 will reintroduce structured headers via rich.panel.Panel.

Dependency

Adds rich>=13.0 to pyproject.toml and requirements.txt. CI installs the wheel, which pulls runtime deps from pyproject — no workflow change needed.

Test plan

• pytest tests/test_logging.py -v (5 new tests: returns logger, env-var level, default INFO, handler idempotence, no propagation)
• Full local suite: 78 passed, 2 xfailed (pre-existing)
• Smoke (default INFO): produces INFO: Loading Expression. style lines, no ANSI escapes
• Smoke (GENEVECTOR_LOG_LEVEL=WARNING): cleanly suppresses INFO output
• CI green across Python 3.9 / 3.10 / 3.11 / 3.12

🤖 Generated with Claude Code