docs: add CONTRIBUTORS.md issues-only policy (closes #1517) (#1604)

* docs: add CONTRIBUTORS.md issues-only policy (#1517)

Document the contribution policy: we accept issues, not pull requests.
Maintainers handle design and implementation through a prompt-driven
workflow. Contributors who have already built a change locally should
share the prompt they used rather than a diff.

Cross-reference the policy from AGENTS.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs: add PR template redirecting external authors to issues-only policy (#1517)

GitHub auto-populates pull_request_template.md into every new PR body,
so it steers would-be external PR authors to CONTRIBUTORS.md before they
submit a diff.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs: drop version-board details from CONTRIBUTORS.md (#1517)

The policy takes effect after v2/main merges into main, leaving a single
line of development. Tell contributors to open a well-formed issue rather
than routing them to per-version project boards.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs: add version-board/label table to CONTRIBUTORS.md (closes #1595)

Completes requirement #2 of #1517: a table mapping each active version to
its base branch, project board, and version label, plus a "Label by
version" note mirroring AGENTS.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S3fTN8H3R8YV4yUGvZjYnX

* docs: drop v1.5 from CONTRIBUTORS.md, invite deeper contribution (#1517)

Review feedback on PR #1604:

- Remove the v1.5 row/bullet from the version table — v1.5 was an internal
  intermediate branch that external contributors never saw, so surfacing it
  in an outward-facing doc is noise. The table is now v1 / v2 only.
- Add a "Want to work on the Inspector with us?" section pointing at the MCP
  Contributor Discord (#inspector-dev) and the community calls, framing the
  issues-only rule as being about unsolicited patches rather than a closed
  door, with supervised work as the path toward maintainership.
- Link that section from "Why this policy exists", and add the same Discord
  pointer to the PR template.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Txmv2qqv3yeKgRzoqXytzD

* docs: drop project-board links from CONTRIBUTORS.md (#1517)

The org project boards aren't visible to anyone outside the organization, so
linking them in an outward-facing doc points contributors at a 404. The
version table is now base branch + label only, and the PR template names the
version labels instead of "the appropriate version board".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Txmv2qqv3yeKgRzoqXytzD

* docs: v1 takes security fixes only (#1517)

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Txmv2qqv3yeKgRzoqXytzD

* docs: use post-runbook branch names (v1/main, main) (#1517)

This doc will be read after the branch runbook completes, when v1 lives on
v1/main and v2 is the default main. Update the version table, the label-by-
version line, and the PR template's label hint + CONTRIBUTORS.md links
accordingly.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Txmv2qqv3yeKgRzoqXytzD

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -102,6 +102,13 @@ After installing, `npm run build` builds all clients. The launcher scripts (`npm
   - v2 - https://github.com/orgs/modelcontextprotocol/projects/28 (active board — all current work goes here)
   - v1 - https://github.com/orgs/modelcontextprotocol/projects/11 (existing inspector version, no new activity except security and bug fixes)
 
+## Contributing
+
+External contributions are accepted as **issues, not pull requests** —
+maintainers handle design and implementation through a prompt-driven workflow.
+If you've already built a change locally, share the **prompt** you used, not a
+diff. See [`CONTRIBUTORS.md`](./CONTRIBUTORS.md) for the full policy.
+
 ## Project Status and Direction
 * The main branch currently contains the legacy version of the Inspector, which we are accepting bug fixes and minor improvement PRs for.