docs: rename repo solstone → solstone-journal (PyPI unchanged)
- README heading: `# solstone` → `# solstone journal` + 1-line journal-layer
framing clause; tagline preserved.
- Update github.com/solpbc/solstone → solstone-journal in README, INSTALL,
CONTRIBUTING, DATA-FLOW, pyproject.toml (project.urls), parakeet hints.
- Migrate vit beacon `vit:github.com/solpbc/solstone` → solstone-journal in
.vit/config.json + solstone/talent/vit/SKILL.md.
PyPI package name unchanged; CHANGELOG historical refs preserved; tests
referencing other solstone-* repos untouched.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>