feature: number-formatting

* feat: Add basic number formatting with tests

* style: Fix SwiftLint warnings in number formatting

* style: Fix multiline parameter brackets formatting

* style: Fix multiline parameter brackets to match SwiftLint rules

* chore: Disable multiline_parameters_brackets rule to resolve SwiftFormat conflict

* style: Fix opening brace placement to match SwiftLint rules

* chore: Disable opening_brace rule to resolve SwiftFormat conflict

* feat: Add core number formatting protocol with decimal support

* feat: Add percentage formatting support

* feat: Add currency formatting support

* feat: Add scientific notation formatting support

* feat: Add ordinal number formatting support

* feat: Add number spelling support

* feat: Add compact notation support

* feat: Add binary formatting support

* feat: Add hexadecimal formatting support

* feat: Add Roman numeral formatting support

* feat: Add octal formatting support

* feat: Add custom base-N formatting support

* feat: Add accounting format support

* feat: Add file size, duration, fraction, and unit formatting

* feat: Add file size, duration, fraction, and unit formatting

* docs: Add comprehensive documentation for number formatting features

* fix: German locale accounting format for currency values

* test: verify German locale accounting format

* style: fix formatting

Author: owdax

.swiftlint.yml

@@ -8,6 +8,8 @@ disabled_rules:
   - trailing_comma
   - comment_spacing
   - switch_case_alignment
+  - multiline_parameters_brackets
+  - opening_brace
 
 opt_in_rules:
   - array_init

Sources/SwiftDevKit/Conversion/NumberFormatting+Numeric.swift

@@ -0,0 +1,68 @@
+// NumberFormatting+Numeric.swift
+// SwiftDevKit
+//
+// Copyright (c) 2025 owdax and The SwiftDevKit Contributors
+// MIT License - https://opensource.org/licenses/MIT
+
+import Foundation
+
+// MARK: - Numeric Types Conformance
+
+extension Int: NumberFormattable {
+    public func formatted(
+        decimals: Int? = nil,
+        grouping: Bool? = nil,
+        roundingRule: NumberFormatter.RoundingMode? = nil) throws -> String
+    {
+        let formatter = NumberFormatter()
+        formatter.numberStyle = .decimal
+        formatter.maximumFractionDigits = decimals ?? 0
+        formatter.usesGroupingSeparator = grouping ?? true
+        formatter.roundingMode = roundingRule ?? .down
+
+        guard let result = formatter.string(from: NSNumber(value: self)) else {
+            throw NumberFormattingError.invalidNumber(String(self))
+        }
+        return result
+    }
+}
+
+extension Double: NumberFormattable {
+    public func formatted(
+        decimals: Int? = nil,
+        grouping: Bool? = nil,
+        roundingRule: NumberFormatter.RoundingMode? = nil) throws -> String
+    {
+        let formatter = NumberFormatter()
+        formatter.numberStyle = .decimal
+        formatter.maximumFractionDigits = decimals ?? 2
+        formatter.minimumFractionDigits = decimals ?? 2
+        formatter.usesGroupingSeparator = grouping ?? true
+        formatter.roundingMode = roundingRule ?? .down
+
+        guard let result = formatter.string(from: NSNumber(value: self)) else {
+            throw NumberFormattingError.invalidNumber(String(self))
+        }
+        return result
+    }
+}
+
+extension Float: NumberFormattable {
+    public func formatted(
+        decimals: Int? = nil,
+        grouping: Bool? = nil,
+        roundingRule: NumberFormatter.RoundingMode? = nil) throws -> String
+    {
+        let formatter = NumberFormatter()
+        formatter.numberStyle = .decimal
+        formatter.maximumFractionDigits = decimals ?? 2
+        formatter.minimumFractionDigits = decimals ?? 2
+        formatter.usesGroupingSeparator = grouping ?? true
+        formatter.roundingMode = roundingRule ?? .down
+
+        guard let result = formatter.string(from: NSNumber(value: self)) else {
+            throw NumberFormattingError.invalidNumber(String(self))
+        }
+        return result
+    }
+}