# 095 — Resolve clippy warnings and make lint enforce a clean run

## Summary

`make lint`'s backend target runs `cargo clippy --all-targets` with no
`-D warnings` (or equivalent), so clippy warnings accumulate silently
instead of failing the lint step. There are currently 23 unique
warnings across 5 lint categories.

## Where

- `Makefile:26` (`lint-be:`) — `cargo clippy --all-targets`, no denial
  flag.
- `cargo clippy --all-targets` currently reports, by lint:
  - `clippy::cloned_ref_to_slice_refs` — 10 occurrences, mostly in
    `src/engine/alerts.rs` test code (e.g. around lines 469, 472, 493,
    534).
  - `clippy::collapsible_if` — 8 occurrences, concentrated in
    `src/engine/snapshot/mod.rs` (lines 608, 940, 961) and
    `src/engine/alerts.rs` (around lines 510, 512).
  - `clippy::type_complexity` — 3 occurrences.
  - `clippy::single_match` — 1 occurrence.
  - `clippy::unnecessary_get_then_check` — 1 occurrence,
    `src/engine/tests.rs:2234`
    (`entries[1].params.get("level").is_none()`).

## Scope

- Fix all 23 current warnings (mechanical for most: `from_ref` for the
  slice-ref clone cases, collapsing nested `if`s, `is_none()` →
  `!contains_key`/`get().is_none()` equivalent simplification per
  clippy's suggestion, breaking up the complex types clippy flags or
  adding a type alias, converting the single-arm `match` to `if let`).
- Once clean, change `Makefile:26` to deny warnings (e.g. `cargo
  clippy --all-targets -- -D warnings`) so the target fails on any
  future regression instead of just printing them.
- Don't add blanket `#[allow(...)]`s to silence these — fix the
  underlying code per clippy's suggestion, matching the existing
  `#[allow(dead_code)]` uses elsewhere in the codebase which are for
  genuinely-unused-for-now items, not a precedent for suppressing
  active lints.