[doc] Convert ray-contribute getting-involved, development, and involvement to MyST

[dstrodtman]

Description

Convert the final three contributor-facing Developer Guides pages in doc/source/ray-contribute/ from reStructuredText to MyST Markdown, completing the section's migration to MyST (the declared standard for new pages). These are the hub/entry pages — the most coupled in the section.

Pages converted:

• getting-involved — the contributor hub
• development — building Ray from source
• involvement — the community-links partial included by getting-involved

Faithful format conversion only — no content restructuring. Notable handling:

• development — the sphinx-design .. tab-set:: / .. tab-item:: and two .. dropdown:: blocks become colon-fence directives (::::{tab-set} / :::{tab-item} / :::{dropdown}) so the nested code fences compose cleanly. All 8 cross-reference labels are preserved (building-ray, fork-ray-repo, prepare-venv, python-develop, python-develop-uninstall, build-distributable-wheel, build-ray-image, full-source-build) — referenced internally and from getting-involved.
• getting-involved — its two .. testcode:: blocks (the canonical pydoc examples) become {testcode}; the page stays excluded from the doctest rule, so its doc/BUILD.bazel exclude entry is updated .rst → .md. The .. include:: of involvement becomes {include} involvement.md, and the shared _includes/_latest_contribution_doc.rst banner stays an include via {include} with :parser: rst. The getting-involved label is preserved.
• involvement — a content partial (no frontmatter); its named-reference links are inlined, which also removes the duplicate on GitHub target it shared with getting-involved.

Companion .claude/ updates point at the new .md paths (root CLAUDE.md, the lint and rebuild skills, the python-guidelines rule). Toctree entries are extensionless and unchanged; .html redirect targets are unaffected.

One forced rendering change: the lettered sub-list (a/b/c) under "Fork the Ray repository" becomes a numbered sub-list (1/2/3), since MyST/CommonMark has no alpha-enumerated lists.

Related issues

None.

Additional information

Verified locally: frontmatter parses; backtick and ::: colon fences balance (60/60 and 10/10); all 9 labels present; {testcode}/{toctree}/{include}/{tab-set}/{tab-item}/{dropdown} counts are exact; no residual RST outside fences; and the blockquote-wrapped code, the Windows nested numbered list, and the python-develop column-0 code-block list all render correctly via markdown-it. The RtD preview build is the authoritative check for the sphinx-design directives and cross-references.

Completes the ray-contribute/ RST→MyST migration (Tier A #64100, Tier B #64111, Tier C #64115, plus the rst-to-myst skill #64135).

Cross-reference fixes (flagged by the initial RtD build): docs.md's link to the renamed getting-involved is now extensionless, and getting-involved's two intra-page section links use MyST #anchor fragments — the original .html#anchor form isn't resolved by MyST and emits myst.xref_missing.

[gemini-code-assist]

Code Review

This pull request converts several documentation files (development, getting-involved, and involvement) from reStructuredText (.rst) to MyST Markdown (.md) and updates all corresponding references across the repository. The review feedback suggests minor improvements to the newly created Markdown files, specifically correcting a duplicate word typo in involvement.md and using relative anchor links instead of hardcoded .html extensions for self-referential links in getting-involved.md.

Important

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[gemini-code-assist]

There is a duplicate "on" in "on [on GitHub]". It should be simplified to "on [GitHub]".

Suggested change

	- Star and follow us on [on GitHub](https://github.com/ray-project/ray).
	- Star and follow us on [GitHub](https://github.com/ray-project/ray).

[gemini-code-assist]

Since this link is self-referential to the same page, you can use relative anchor links (#testing and #lint-and-formatting) instead of hardcoding the .html filename extension.

Suggested change

	2. Make sure all existing [tests](getting-involved.html#testing) and [linters](getting-involved.html#lint-and-formatting) pass.
	2. Make sure all existing [tests](#testing) and [linters](#lint-and-formatting) pass.