Initialise the project per the approved implementation plan (M0).
- Pin the toolchain with devbox: Rust 1.97.1, pimsync 0.5.11, jujutsu 0.44.0,
and radicale 3.7.8 for later integration tests.
- Add the configuration model with full referential validation, reporting
every problem in one pass rather than short-circuiting on the first.
- Add `calcalist doctor`, verifying pimsync's presence and version series,
the state directory, and the configuration.
- Define the whole CLI surface; only `doctor` acts, the rest exit 2 rather
than pretending to work.
- Rewrite SPECS.md: Rust naming conventions in place of the JS/TS style
lines, a `devbox run check` gate instead of a pre-commit hook (jj runs no
git hooks), and the sync semantics the spec previously left unstated.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
