docs: point repo references at slackapi/slack-skills-plugin

[mwbrooks]

Summary

We have renamed our GitHub repo from slackapi/slack-mcp-plugin to slackapi/slack-skills-plugin to capture the MCP & Skills AI Coding Agent Plugin feature set. This pull request updates the repo's docs files to match the new name:

• Update the homepage field in .claude-plugin/plugin.json to point at slackapi/slack-skills-plugin (the repo's new name).
• Update the CI badge in README.md, the Contributing Guidelines link in the PR template, and the repo reference in the maintainers guide.
• Fix 4 pre-existing broken slack-mcp-cursor-plugin Issues links in .github/contributing.md while we're touching related files.

The historical changeset entry at .changeset/fix-plugin-homepage.md is intentionally left as-is since it describes a past fix.

Env vars (SLACK_MCP_TOKEN, SLACK_MCP_URL) are intentionally unchanged - they refer to the Slack-hosted MCP server, not this plugin.

Preview

N/A - text-only changes to docs and metadata; no user-facing UI to preview.

Testing

• grep -rn "slack-mcp-plugin\|slack-mcp-cursor-plugin" --include='*.md' --include='*.json' --include='*.toml' --include='*.yml' --include='*.py' --include='Makefile' . returns only the historical .changeset/fix-plugin-homepage.md entry.
• .claude-plugin/plugin.json remains valid JSON (python3 -c "import json; json.load(open('.claude-plugin/plugin.json'))").
• After merge, confirm the README badge on GitHub renders and links to the new repo's Actions page.

Notes

• User installs and updates will continue working via GitHub's automatic redirect from the old repo URL.
• Contributors may want to run git remote set-url origin https://github.com/slackapi/slack-skills-plugin.git to update it.

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run make test and the tests pass.

[changeset-bot]

🦋 Changeset detected

Latest commit: 1b4e4de

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
slack	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[mwbrooks]

Comments for the kind reviewers

[mwbrooks]

note: This was the repo's name before it's previous rename 😆

[zimeg]

📚 🔏 @mwbrooks LGTM! Thanks for moving this forward to a more final state 🏁 ✨

[WilliamBergamin]

Praise for these changes 🙏 I have one none blocking question for you 🤔

In the README.md should we rename # Slack MCP and Skills Plugin → # Slack Skills Plugin

[mwbrooks]

Praise for these changes 🙏 I have one none blocking question for you 🤔

In the README.md should we rename # Slack MCP and Skills Plugin → # Slack Skills Plugin

Thanks for the positive vibes @WilliamBergamin ⚡ Good question about the README.md. I'd like to intentionally keep it as # Slack MCP and Skills Plugin. I think the MCP feature and keyword are strong and important. The term skills is emerging as a common phrase for Claude/Codex plugins but it's not mainstream. In order for people to find this repo organically, I'd like to include MCP in the title for a while.

[mwbrooks]

Thanks for the reviews @zimeg @WilliamBergamin! 🙇🏻