fix: add bounds check in ProcessSnippetInjection to prevent IndexOutOfRangeException

[gavinbarron]

Problem

The Generate snippets pipeline step crashes with:

System.AggregateException: One or more errors occurred. (Index was outside the bounds of the array.)
 ---> System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at ApiDoctor.ConsoleApp.Program.ProcessSnippetInjection(...)

Root Cause

In ProcessSnippetInjection, the FindEndOfTabSection state accesses originalFileContents[currentIndex + 1] without bounds checking. When a markdown file's tab section terminator --- is the very last line with no trailing blank line, this throws an IndexOutOfRangeException.

Fix

Added a bounds check (\currentIndex + 1 < originalFileContents.Length) before accessing the next array element.

Tests

• *\ExistingTabSection_DashesAsLastLine_DoesNotThrow* — reproduces the exact pipeline crash scenario
• *\FirstInsertion_CommentOnFirstLine_DoesNotThrow* — covers the
  equestStartLine - 1\ edge case

[Copilot]

Pull request overview

Fixes a crash in the snippet-injection pipeline by preventing an out-of-bounds array access when a markdown tab section terminator (---) is the last line of a file.

Changes:

• Add a bounds check before reading originalFileContents[currentIndex + 1] when detecting the end of a tab section.
• Add unit tests covering the EOF --- scenario and an additional “comment on first line” edge-case scenario.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
ApiDoctor.Console/Program.cs	Adds bounds check in the tab-section end detection to avoid IndexOutOfRangeException.
ApiDoctor.Console.UnitTests/ProcessSnippetInjectionTests.cs	Adds tests intended to reproduce the EOF --- crash scenario and cover an additional edge case.

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