This is phase 1 of the namespace refactor required before distributing the project on PyPI as solstone. The five previous top-level packages (think, apps, observe, convey, talent) collide with unrelated PyPI projects, so a pip install solstone layout would clobber those packages instead of installing a single coherent distribution. Move the Python package tree under solstone/, rewrite imports and runtime module strings, and update packaging, Makefile targets, scripts, tests, docs, and package data declarations to match the new canonical module paths. Audit and fix Path(__file__) walks for the new layout, with get_project_root() now correctly anchored at the repository root. Preserve callosum event taxonomy, provider routing keys, journal config keys, journal data layout, and on-disk historical content. This is a clean break: no back-compat shims, aliases, fallbacks, or re-exports. Phase 2 will handle the PyPI publish work; phase 3 will handle the INSTALL.md distribution rewrite. Co-Authored-By: Codex <codex@openai.com>