Replace meval with evalexpr, add tests and CI (0.1.12)

[binarypie]

Summary

Two related changes:

1. Calculator: meval → evalexpr. meval 0.2 is unmaintained and pulled in an ancient nom 1.2 that triggered a future-incompatibility warning. Switched to the actively maintained evalexpr, removing that warning.
2. Test coverage + CI. Added unit/integration tests across the codebase and a GitHub Actions workflow to run them.

Calculator behaviour preserved

evalexpr differs from meval in two ways that matter for a calculator; both are handled so existing expressions keep working:

• Float division. evalexpr does integer division for integer operands (5/2 == 2). Bare integer literals are coerced to floats before evaluation so arithmetic behaves like a calculator (5/2 == 2.5). Digits that belong to identifiers (the 10 in log10) or decimal literals (3.14) are left untouched.
• Functions & constants. evalexpr only exposes math functions under a math:: namespace and ships no math constants. A custom evaluation context registers the familiar bare names (sqrt, sin, cos, tan, ln, log, log2, log10, exp, abs, floor, ceil, round, pow, ...) and the constants pi, e, tau.

Division by zero still yields Infinity, matching the previous f64 behaviour.

Tests

cargo test now runs 30 tests:

• calculator — literal floatification, arithmetic, functions/constants, error handling, result formatting
• applications — AppSource detection, .desktop parsing (incl. NoDisplay / missing-Exec skips), bulk loading from an extra dir, query matching (name, id, no-match, empty-query truncation)
• config — defaults, TOML round-trip, serde fallback for partial/empty configs
• providers — Item builder and Item / ProviderInfo → protobuf conversions
• manager — registration, score-based combining/sorting, max_results truncation, explicit-provider filtering, prefix routing (via a mock provider)
• server — end-to-end query and list-providers round-trips over a real Unix socket

CI

Adds .github/workflows/ci.yml — on pushes to main and on PRs it installs protoc, then runs cargo fmt --check, cargo build --locked, and cargo test --locked.

Verification

• cargo build --release --locked ✅
• cargo test ✅ (30 passed)
• cargo fmt --all -- --check ✅
• meval and the old nom 1.2 are gone from Cargo.lock; future-incompat warning resolved

Bumps version to 0.1.12 (Cargo.toml + datacube.spec).

https://claude.ai/code/session_01B33sAdjSZQQ6XRtFkxYTAb