Establishes the cargo workspace and the shared `blocker-core` crate. The
engine is deliberately written before any platform code, because CLAUDE.md
section 2 makes it the single source of decision truth and M1 acceptance
requires it to be pure.
**Workspace** — five crates plus a test crate, zero external dependencies.
Section 3 requires every crate to justify its binary-size cost, so M0 adds
none. [profile.release] is workspace-only (cargo rejects it in members) and
carries the section 5 settings that make the 5 MB stripped budget reachable.
**Purity contract** — `evaluate(&EngineInput) -> Decision` reads no clock, no
disk and no OS API; everything arrives in the input. `tests/purity.rs`
enforces this mechanically by asserting blocker-core has zero dependencies, so
a stray I/O reach-in fails the build rather than silently making the golden
tables useless as a parity contract.
Decisions worth calling out:
- **Monotonic time is a separate type from wall time.** Section 1.5.3 requires
a system date change never to shorten a lock. Keeping them apart makes that
structural rather than a rule to remember.
- **`start > end` means overnight.** No `crosses_midnight` flag: the comparison
already encodes it and a second field is a second way to be wrong. The
weekday for a window that started yesterday evening is yesterday's, which
`overnight_window_survives_past_midnight` pins down.
- **`next_wakeup` is armed over every non-paused schedule, not only active
ones.** Filtering to active conditions first would let the daemon sleep
straight through the moment a schedule is due to start.
- **Allowlist needs the installed-app inventory.** `EngineInput` carries
`installed_apps`; an empty slice fails open rather than guessing.
- **Wall-clock correction extends, never shortens, and clamps to the 24h cap.**
Extending unbounded would satisfy anti-tamper and violate section 1.5.4.
- **`cast_possible_truncation` is denied workspace-wide.** Truncating a
millisecond counter would corrupt a lock timer.
Verified: 22 tests pass, `cargo fmt --check` clean, `cargo clippy -D warnings`
clean, stripped release daemon 0.279 MB against the 5 MB budget.
Co-Authored-By: Claude Code <noreply@anthropic.com>
