[WIP] Update README with clear installation instructions and references

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

The README.md file in the fix-readme-conflicts branch contains unresolved merge conflicts that need to be cleaned up and updated. Consolidate the content so that the README provides clear and consistent installation instructions, references to the skill marketplace, and documentation links.

Key steps:

1. Remove all conflict markers (<<<<<<<, =======, >>>>>>>), and ensure the final installation content is complete and reflects the latest instructions.
2. Ensure that the 'Installation Instructions' section includes the following installation methods:
   • Skilz CLI installations for multiple agents (Claude Code, OpenCode, OpenAI Codex, and Gemini).
   • Claude Desktop installation.
   • Manual installation using git clone commands.
   • GitHub URL-based skilz installation (skilz install -g).
3. Ensure all references, including the Skilz CLI user guide and skill marketplace link, are included and correctly formatted.

Update the README.md file to address these issues and prevent confusion for readers.

After resolving and cleaning the README conflicts, submit these updates as a new pull request to merge into the main branch.

This pull request was created from Copilot chat.

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