docs: add macOS first-run prerequisites to quick start

[WuKongAI-CMU]

Summary\n- add macOS first-run prerequisites to the quick start\n- document Xcode Command Line Tools, container runtime expectations, and recommended setup order\n- capture common first-run failures before the install steps\n\n## Linked issue\n- closes #814\n\nReplacement for auto-closed #905 after the contributor open-PR limit was hit.

Summary by CodeRabbit

• Documentation
  • Added a macOS first-run checklist under Prerequisites to guide initial environment setup
  • Checklist outlines required steps: install Xcode Command Line Tools, set up a supported container runtime (Docker Desktop or Colima), then run the installer
  • Highlights common first-run issues to avoid: missing developer tools and Docker connection errors when no runtime is installed or running

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between b42f291 and 2cbe41f.

📒 Files selected for processing (1)

• README.md

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📝 Walkthrough

Walkthrough

A new macOS first-run checklist section was added to the README prerequisites, documenting the recommended installation sequence for fresh macOS machines: install Xcode Command Line Tools, install a supported container runtime, then run the NemoClaw installer.

Changes

Cohort / File(s)	Summary
macOS First-Run Setup Documentation README.md	Added a dedicated macOS first-run checklist section under prerequisites, outlining the recommended installation order and documenting two common failure categories (missing Xcode Command Line Tools and missing container runtime).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 A checklist hops onto the page,
For Macs fresh as a blank stage,
Xcode first, then runtime too—
No more guessing what to do! 🚀

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding macOS first-run prerequisites documentation to the quick start guide, which matches the file change (README.md update).
Linked Issues check	✅ Passed	All primary objectives from linked issues #814 and #905 are met: macOS first-run prerequisites section added to README, Xcode Command Line Tools requirement documented, supported container runtimes listed, recommended install order provided, and common first-run failures identified.
Out of Scope Changes check	✅ Passed	The pull request contains only documentation changes (README.md) directly related to the linked issues; no out-of-scope code modifications or unrelated content is present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

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[WuKongAI-CMU]

This replacement PR is current on main and ready for human review when maintainers have a cycle. I intentionally kept it scoped to the first-run macOS prerequisites only.

[prekshivyas]

Clean, accurate, well-scoped. The checklist matches the supported runtimes in the Container Runtime table and the placement after that table is natural.

One optional follow-up: adding an xcode-select troubleshooting entry to docs/reference/troubleshooting.md would round out the macOS coverage, but that's not a blocker for this PR.