style: Migrate to stable-only rustfmt configuration

- Remove nightly-only features from .rustfmt.toml and vendor/ss58-registry/rustfmt.toml
- Removed features: imports_granularity, wrap_comments, comment_width,
  reorder_impl_items, spaces_around_ranges, binop_separator,
  match_arm_blocks, trailing_semicolon, trailing_comma
- Format all 898 affected files with stable rustfmt
- Ensures long-term reliability without nightly toolchain dependency

bizinikiwi/primitives/arithmetic/src/biguint.rs

@@ -273,9 +273,9 @@ impl BigUint {
 			let mut k = 0;
 			for i in 0..m {
 				// PROOF: (B−1) × (B−1) + (B−1) + (B−1) = B^2 −1 < B^2. addition is safe.
-				let t = mul_single(self.get(j), other.get(i)) +
-					Double::from(w.get(i + j)) +
-					Double::from(k);
+				let t = mul_single(self.get(j), other.get(i))
+					+ Double::from(w.get(i + j))
+					+ Double::from(k);
 				w.set(i + j, (t % B) as Single);
 				// PROOF: (B^2 - 1) / B < B. conversion is safe.
 				k = (t / B) as Single;

bizinikiwi/primitives/arithmetic/src/per_things.rs

@@ -490,10 +490,12 @@ impl Rounding {
 		match (rounding, negative) {
 			(Low, true) | (Major, _) | (High, false) => Up,
 			(High, true) | (Minor, _) | (Low, false) => Down,
-			(NearestPrefMajor, _) | (NearestPrefHigh, false) | (NearestPrefLow, true) =>
-				NearestPrefUp,
-			(NearestPrefMinor, _) | (NearestPrefLow, false) | (NearestPrefHigh, true) =>
-				NearestPrefDown,
+			(NearestPrefMajor, _) | (NearestPrefHigh, false) | (NearestPrefLow, true) => {
+				NearestPrefUp
+			},
+			(NearestPrefMinor, _) | (NearestPrefLow, false) | (NearestPrefHigh, true) => {
+				NearestPrefDown
+			},
 		}
 	}
 }