Add AGENTS.md with repository-specific agent operating guidance

[Copilot]

Adds an AGENTS.md at the repository root to provide a single, repo-scoped contract for automated contributors. The document captures how to work in this codebase without rediscovering conventions each run.

• Scope and purpose

  • Introduces /AGENTS.md describing the repository’s Wordle solver context and expected working boundaries.

• Execution baseline

  • Documents Python/runtime expectations and standard dependency installation from repo root.

• Operational commands

  • Captures canonical commands for running the solver, unit tests, and linting aligned with existing project usage.

• Change guardrails

  • Defines concise constraints for safe edits (minimal scope, no generated artifacts, preserve CLI behavior unless requested, update tests when solver logic changes).

• Repo-specific pointers

  • Notes key locations and CI workflows relevant to contributors (word lists, Pylint/CodeQL/Qodana presence).

## Common Commands
- Run solver:
  - `python /home/runner/work/wordle/wordle/src/wordle.py -d /home/runner/work/wordle/wordle/words/wordle-nyt-words-14855.txt`
- Run unit tests:
  - `PYTHONPATH=/home/runner/work/wordle/wordle/src python -m unittest /home/runner/work/wordle/wordle/src/solvertests.py`