fix: clippy single_match in heph-tui + add clippy pre-commit hook

CI on main failed on a clippy::single_match lint in the heph-tui sidebar
key handler. Rewrite as `if let`. Also add a `cargo clippy -D warnings`
prek hook mirroring cargo-fmt, so lints are caught locally before CI
(prek previously only ran cargo fmt).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/heph-tui/src/main.rs

@@ -186,10 +186,11 @@ fn handle_key<B: heph_tui::Backend>(app: &mut App<B>, key: KeyEvent) -> Option<A
                 KeyCode::Char('D') => app.begin_delete(),
                 _ => {}
             },
-            Focus::Sidebar => match key.code {
-                KeyCode::Char('D') => app.begin_delete_project(),
-                _ => {}
-            },
+            Focus::Sidebar => {
+                if let KeyCode::Char('D') = key.code {
+                    app.begin_delete_project()
+                }
+            }
         },
     }
     None

docs/changelog.d/+clippy-prek-hook.infra.md

@@ -0,0 +1 @@
+Add a `cargo clippy -D warnings` pre-commit hook so lints are caught locally before CI.

docs/changelog.d/+fix-clippy-single-match.bugfix.md

@@ -0,0 +1 @@
+Fix `clippy::single_match` lint in heph-tui sidebar key handling (CI failure on main).

prek.toml

@@ -97,6 +97,18 @@ language = "system"
 files = '\.rs$'
 pass_filenames = false
 
+# Rust linting - cargo clippy over the whole workspace, denying warnings to
+# match CI (`dagger call check` / .forgejo/scripts/build run the same command).
+# Catches lints (e.g. clippy::single_match) before they reach CI. Uses the
+# system toolchain; runs whenever a .rs file is staged.
+[[repos.hooks]]
+id = "cargo-clippy"
+name = "cargo-clippy"
+entry = "cargo clippy --all-targets --all-features -- -D warnings"
+language = "system"
+files = '\.rs$'
+pass_filenames = false
+
 # GitHub/Forgejo Actions workflow linting
 [[repos]]
 repo = "https://github.com/rhysd/actionlint"