style(mcp): wrap staleMarkerSuffix to satisfy MaxLineLength

Line 18 was 131 chars after the staleMarkerSuffix extraction
(8490db7), tripping detekt's 120-char rule. Gradle's local detekt
cache hit hid the issue until CI saw a cold cache. Split the
expression across two lines so the rule passes without a baseline
exemption.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: beyondwin

fixthis-mcp/src/main/kotlin/io/github/beyondwin/fixthis/mcp/session/FormatterExtensions.kt

@@ -15,7 +15,8 @@ internal fun SourceCandidate.fileWithLineAndOwner(): String {
     return "${fileWithLine()}$ownerSegment"
 }
 
-internal fun SourceCandidate.staleMarkerSuffix(): String = if (stale == true) " ⚠ stale: ${staleReason ?: "unspecified"}" else ""
+internal fun SourceCandidate.staleMarkerSuffix(): String =
+    if (stale == true) " ⚠ stale: ${staleReason ?: "unspecified"}" else ""
 
 internal fun FixThisRect.formatBounds(): String = "$left,$top,$right,$bottom"