fix: clamp ProgressBar barLength to non-negative value to avoid crash (#1525)

- Closes #1547.
- A negative progress value (e.g. from a race in progress events) would
produce a negative barLength and crash inside String(repeating:count:).
Wrap the computed length in max(0, ...) and add a regression test that
calls set(size: -10) and exercises draw(state:detail:).

Sources/TerminalProgress/ProgressBar.swift

@@ -275,7 +275,7 @@ extension ProgressBar {
             // 45 reserves space for components rendered after the bar (size, speed, time, etc.)
             let usedWidth = (useColor ? joinedComponents.visibleLength : joinedComponents.count) + 45
             let remainingWidth = max(config.width - usedWidth, 1)
-            let barLength = min(remainingWidth, state.finished ? remainingWidth : Int(Int64(remainingWidth) * value / total))
+            let barLength = min(remainingWidth, max(0, state.finished ? remainingWidth : Int(Int64(remainingWidth) * value / total)))
             let barPaddingLength = remainingWidth - barLength
             if useColor {
                 let filledBar = EscapeSequence.colored(String(repeating: config.theme.bar, count: barLength), EscapeSequence.green)

Tests/TerminalProgressTests/ProgressBarTests.swift

@@ -749,6 +749,22 @@ final class ProgressBarTests: XCTestCase {
         let _ = progress.draw()
     }
 
+    func testProgressBarNegativeValue() async throws {
+        // Regression test: a negative progress value (e.g. from a race in progress events)
+        // must not cause String(repeating:count:) to be called with a negative count.
+        let config = try ProgressConfig(
+            description: "Task",
+            showProgressBar: true,
+            totalSize: 50,
+            width: 57
+        )
+        let progress = ProgressBar(config: config)
+        progress.set(size: -10)
+        // draw(state:detail:) should clamp barLength to [0, remainingWidth] and not crash.
+        let state = progress.state.withLock { $0 }
+        let _ = progress.draw(state: state, detail: .full)
+    }
+
     func testItemsName() async throws {
         let config = try ProgressConfig(
             description: "Task",