docs: rename CONTRIBUTORS.md to CONTRIBUTING.md so GitHub surfaces the policy

[cliffhall]

Closes #1883

Sub-task of #1821.

What changed

• git mv CONTRIBUTORS.md CONTRIBUTING.md — a pure rename, zero content changes (git show --stat reports CONTRIBUTORS.md => CONTRIBUTING.md | 0), so history follows the file. Its heading already reads "Contributing to MCP Inspector".
• AGENTS.md — the one in-repo reference, in the Contributing section:
  See [CONTRIBUTORS.md](./CONTRIBUTORS.md) for the full policy. → See [CONTRIBUTING.md](./CONTRIBUTING.md) for the full policy.

I re-grepped (git grep -n CONTRIBUTORS) across .github/, README.md, docs/, clients/*/README.md, and specification/. On v2/main today the only other hits are the two links in .github/pull_request_template.md, which are deliberately left alone — open PR #1879 makes both of them relative so they follow the rename automatically, and editing them here would collide with it. (There is no SECURITY.md on v2/main, so nothing to sweep there.)

Why it matters

GitHub's contributing-guidelines affordance — the banner surfaced when someone clicks New issue or opens a pull request — keys on the exact filename CONTRIBUTING.md. v2 named the file CONTRIBUTORS.md, so that prompt was dark in exactly the place the "open an issue, not a PR" policy needs to land. Renaming lights it up, and it removes the need for the redirect-stub alternative considered in #1870 (which would have left two files to keep in sync).

⚠️ Dependency on #1866 — required post-merge sweep

PR #1866 (v2/docs/post-swap-branch-model-and-pr-policy) modifies both CONTRIBUTORS.md and AGENTS.md, and merges before this one. This PR is branched from v2/main, not stacked on #1866, per the plan in #1883.

Git resolves the rename/modify pair on the file itself automatically (rename detection replays #1866's edits onto CONTRIBUTING.md), so the renamed file is not the problem. What is a problem: #1866 introduces a new reference to the old filename that does not exist on v2/main yet, so it cannot be fixed in this PR. After both land, sweep it:

File	Line #1866 introduces (quoted)	Fix
AGENTS.md	If you've already built a change locally, share the **prompt** you used and screenshots if applicable, not a diff. See [`CONTRIBUTORS.md`](./CONTRIBUTORS.md) for the full policy.	Replace both the link text and the target with CONTRIBUTING.md

That is the complete list — gh pr diff 1866 touches four files (.github/copilot-instructions.md, AGENTS.md, CONTRIBUTORS.md, README.md) and the only added line mentioning the old name is the AGENTS.md one above. (The other CONTRIBUTORS.md occurrences in that diff are the removed original of this same line and the diff's own a//b/ path headers, which the rename handles.)

Note also that #1866 rewrites the very line this PR edits, so if git flags a textual conflict in AGENTS.md, resolve it by taking #1866's rewritten sentence with CONTRIBUTING.md substituted for CONTRIBUTORS.md — i.e. exactly the table row above.

Known, accepted breakage

External links to blob/*/CONTRIBUTORS.md — including in already-posted PR/issue comments — will 404. GitHub does not redirect deleted paths; this is called out and accepted in #1883.

Testing

Docs-only rename; no code paths touched, so no build/test surface is affected.

🤖 Generated with Claude Code

https://claude.ai/code/session_01YAt8rqxysNbhYWLhoRm3fU

[Copilot]

Pull request overview

Renames the repository’s contributing-policy document to CONTRIBUTING.md so GitHub’s built-in contributing-guidelines affordance is enabled, and updates the in-repo reference in AGENTS.md to match the new filename.

Changes:

• Adds/renames the contributing guidelines document to CONTRIBUTING.md.
• Updates AGENTS.md to link to CONTRIBUTING.md instead of CONTRIBUTORS.md.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 1 comment.

File	Description
CONTRIBUTING.md	Contributing policy document intended to be surfaced by GitHub’s UI.
AGENTS.md	Updates the contributing-policy link to the new filename.

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[cliffhall]

Correct observation, but intentionally out of scope here — declining in this PR.

.github/pull_request_template.md is already owned by open PR #1879, which converts both of its links to repo-relative form so they follow this rename automatically. Editing the same two lines here would collide with that PR for no benefit, so #1883 explicitly scopes them out ("#1879 already handles the PR-template links... Don't re-fix them here").

The redirect-stub alternative you mention was considered in #1870 and rejected — it leaves two files to keep in sync, which is exactly what this rename removes.

Sequencing, so nothing is left dangling: #1879 lands the relative links, this PR lands the rename, and the PR body enumerates the one remaining post-merge sweep item (the new CONTRIBUTORS.md reference that #1866 adds to AGENTS.md, which doesn't exist on v2/main yet and so can't be fixed from this branch).

[cliffhall]

Reduced to a pure rename so this can't conflict with #1866.

The AGENTS.md link edit is gone from this PR. #1866 rewrites that exact line, so keeping it here guaranteed a one-line conflict at merge time; instead #1866 now writes the link as CONTRIBUTING.md itself (its commit). The two PRs now share no file and no line.

This also retires the post-merge sweep enumerated in the description above — there is nothing left to sweep, since the one reference #1866 introduces already points at the new name.

Tradeoff, stated plainly: between #1866 merging and this merging, AGENTS.md links to a filename that doesn't exist yet. That window is deliberate and bounded — #1866 is first in #1821's merge order and this is third.

Note the rename/modify relationship still exists at the git level (#1866 edits CONTRIBUTORS.md's contents; this renames it). That's the case git's rename detection resolves automatically, applying #1866's edits to the renamed file. What's been eliminated is the line-level conflict, which git could not have resolved on its own.