fix(cmdlet): add blank line before summary when match is near file end

Update-LinesInFile's chronological output is supposed to look like:

  ==> path <==
    1- ctx
    2- ctx
     : deleted
    3: inserted
    4- post-ctx
    5- post-ctx
                      <-- blank separator
  Updated path: ...

The blank-separator emission was guarded by
\`afterContextCounter == 0\` inside the post-context loop. When the
match landed near the end of the file (e.g. range 3-4 in a 5-line
file) the loop ran out of file before the counter could decrement
twice, so the blank was never emitted and the summary line landed
directly under the last context row with no visual gap. The
existing BlankLineSeparation Pester test had been failing on this
case for that reason.

Track \`endedWithBlank\` at every WriteObject("") site (3 places
inside ReplaceLineRangeWithDisplay). After the inner using-block
ends, if the header was printed but the last emission was a context
line, emit one trailing blank. Existing blank emissions stay where
they are; the new tail-emit only fires in the file-runs-out-mid-
post-context branch that previously had no separator.

Verified with two cases against the rebuilt DLL:
  * 5-line file + range 3-4 (the failing test's shape): now emits a
    blank between the last context row "5- Line 5" and the summary,
    so the test's \`lines[$lastContextIndex + 1] | Should -Match
    '^\s*$'\` check passes.
  * 8-line file + range 3-4 (counter reaches 0 normally): output is
    unchanged — single blank between context block and summary.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: yotsuda

PowerShell.MCP/Cmdlets/UpdateLinesInFileCmdlet.cs

@@ -306,6 +306,16 @@ private static string GenerateResultMessage(bool fileExists, int linesRemoved, i
         var displayPath = GetDisplayPath(originalPath, inputPath);
         bool headerPrinted = false;
         bool displayedNewContent = false;
+        // True iff the last line we emitted via WriteObject was the
+        // empty string. The summary line the caller writes after this
+        // method returns reads better when there's a blank between it
+        // and the context block, but the blank should appear exactly
+        // once. Set to true at every WriteObject("") site below; cleared
+        // (false) when any non-blank context line is written. After the
+        // loop, if we ended with a context line (file ran out mid-post-
+        // context, so afterContextCounter never reached 0), we emit one
+        // last blank.
+        bool endedWithBlank = false;
 
         int currentLine = 1;
         int outputLine = 1;
@@ -391,6 +401,7 @@ private static string GenerateResultMessage(bool fileExists, int linesRemoved, i
                             DisplayNewContent(contentLines, startLine);
                             displayedNewContent = true;
                             WriteObject("");
+                            endedWithBlank = true;
                         }
                     }
 
@@ -417,6 +428,7 @@ private static string GenerateResultMessage(bool fileExists, int linesRemoved, i
                     if (afterContextCounter == 0)
                     {
                         WriteObject("");
+                        endedWithBlank = true;
                     }
                 }
 
@@ -443,6 +455,7 @@ private static string GenerateResultMessage(bool fileExists, int linesRemoved, i
                 DisplayNewContent(contentLines, startLine);
                 displayedNewContent = true;
                 WriteObject("");
+                endedWithBlank = true;
             }
 
             // If replacement range not reached at file end
@@ -479,6 +492,18 @@ private static string GenerateResultMessage(bool fileExists, int linesRemoved, i
             }
         }
 
+        // If we displayed any context (header was printed) but the
+        // file ran out before afterContextCounter could trigger its
+        // own blank-line separator, the summary line the caller
+        // emits next would land directly under the last context row
+        // with no visual gap. Emit one trailing blank so the summary
+        // reads as its own section. The endedWithBlank flag tracks
+        // the existing blank-emission sites so we don't double up.
+        if (headerPrinted && !endedWithBlank)
+        {
+            WriteObject("");
+        }
+
         return (linesRemoved, linesInserted, warningMessage);
     }