style: format the whole tree with cargo fmt (stock defaults, #35)

One-time, mechanical reformat — no functional changes. The tree was not
rustfmt-clean (~1800 hunks across ~100 files); this brings it to stock
`cargo fmt` defaults so a `cargo fmt --check` CI gate can follow.
Behaviour-preserving: 2509 pass / 0 fail / 1 ignored (unchanged baseline),
clippy clean. A .git-blame-ignore-revs entry follows so `git blame`
skips this commit.

src/type_change.rs

@@ -87,9 +87,7 @@ pub fn static_refusal(src: Type, target: Type) -> Option<String> {
 }
 
 const fn is_in_matrix(src: Type, target: Type) -> bool {
-    use Type::{
-        Bool, Date, DateTime, Decimal, Int, Real, Serial, ShortId, Text,
-    };
+    use Type::{Bool, Date, DateTime, Decimal, Int, Real, Serial, ShortId, Text};
     matches!(
         (src, target),
         // Always-clean transformers
@@ -130,9 +128,7 @@ pub fn transform_cell(src: Type, target: Type, value: &Value) -> CellOutcome {
     if matches!(value, Value::Null) {
         return CellOutcome::Clean(Value::Null);
     }
-    use Type::{
-        Bool, Date, DateTime, Decimal, Int, Real, Serial, ShortId, Text,
-    };
+    use Type::{Bool, Date, DateTime, Decimal, Int, Real, Serial, ShortId, Text};
     match (src, target) {
         // ---- Always-clean: int / serial source ----
         (Int | Serial, Real) => match value {
@@ -179,9 +175,11 @@ pub fn transform_cell(src: Type, target: Type, value: &Value) -> CellOutcome {
         (Bool, Text) => match value {
             // "true" / "false" matches the DSL boolean grammar
             // (ADR-0014 §5), not raw 0/1 stringification.
-            Value::Integer(i) => CellOutcome::Clean(Value::Text(
-                if *i == 0 { "false".into() } else { "true".into() },
-            )),
+            Value::Integer(i) => CellOutcome::Clean(Value::Text(if *i == 0 {
+                "false".into()
+            } else {
+                "true".into()
+            })),
             other => unexpected_storage("bool", other),
         },
 
@@ -369,9 +367,7 @@ pub fn transform_cell(src: Type, target: Type, value: &Value) -> CellOutcome {
                     }
                 } else {
                     CellOutcome::Incompatible {
-                        reason: format!(
-                            "`{s}` is not a datetime in `YYYY-MM-DDTHH:MM:SS` form"
-                        ),
+                        reason: format!("`{s}` is not a datetime in `YYYY-MM-DDTHH:MM:SS` form"),
                     }
                 }
             }
@@ -450,10 +446,7 @@ fn real_to_int(r: f64) -> CellOutcome {
         let discarded = r - r.trunc();
         CellOutcome::Lossy {
             new: Value::Integer(truncated),
-            reason: format!(
-                "truncated; would discard {}",
-                format_real(discarded)
-            ),
+            reason: format!("truncated; would discard {}", format_real(discarded)),
         }
     }
 }
@@ -555,9 +548,7 @@ fn format_real(r: f64) -> String {
 
 fn unexpected_storage(label: &str, value: &Value) -> CellOutcome {
     CellOutcome::Incompatible {
-        reason: format!(
-            "internal: cell stored unexpectedly for `{label}` source ({value:?})"
-        ),
+        reason: format!("internal: cell stored unexpectedly for `{label}` source ({value:?})"),
     }
 }
 
@@ -638,7 +629,10 @@ mod tests {
             (Type::Date, Type::Int),
             (Type::ShortId, Type::Int),
         ] {
-            assert!(static_refusal(src, target).is_some(), "{src:?} -> {target:?}");
+            assert!(
+                static_refusal(src, target).is_some(),
+                "{src:?} -> {target:?}"
+            );
         }
     }
 
@@ -672,7 +666,10 @@ mod tests {
             (Type::Bool, Type::Real),
         ];
         for (s, t) in pairs {
-            assert_eq!(transform_cell(s, t, &Value::Null), CellOutcome::Clean(Value::Null));
+            assert_eq!(
+                transform_cell(s, t, &Value::Null),
+                CellOutcome::Clean(Value::Null)
+            );
         }
     }