Select tasks by task_name frontmatter field instead of filename

[Copilot]

• Explore repository structure and understand current task selection mechanism
• Run existing tests to verify baseline functionality
• Modify task selection logic to use front-matter task_name instead of filename
• Add validation: error if multiple files have the same task_name (without selectors)
• Add validation: error if task file is missing task_name in front-matter
• Implement selector-based filtering for tasks (allowing multiple prompts for one task)
• Update all existing tests to include task_name in front-matter
• Add new tests to verify task selection behavior
• Update documentation
• Final testing and verification
• Address code review feedback:
  • Changed from array to single string variable for matching task file
  • Error immediately on duplicate match instead of collecting all matches
  • Removed taskFileErrors array, return first error immediately
  • Simplified selector matching by using includes directly (task_name already in includes)

Original prompt

Modify the code so that we can select tasks in the same way as we select rule. This will allow mulitple prompts for one task. Use front-matter. Have a front-matter named "task_name" and select on that. If more than one file matches, that is an error. If the taskfile is missing the task_name, that's also an error. Finally, the name of the file does matter anymore.

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[alexec]

@copilot make the requested changes.

[Copilot]

@copilot make the requested changes.

All requested changes have been made in commit abc03a9:

• Using single string variable instead of array for matching task file
• Returning first error immediately instead of collecting errors
• Simplified selector matching by using includes directly

All tests pass and manual verification confirms the behavior works correctly.