docs: add guidance on discussing features before opening PRs

[felixweinberger]

Expands CONTRIBUTING.md with clear guidance on the contribution process.

Motivation and Context

We've been getting PRs for features that weren't previously discussed, leading to wasted effort on both sides. This document sets clear expectations.

Key Changes

• Warmer opening: "Welcome, and thanks for your interest in contributing!"
• Issues section: "Discuss Before You Code" policy, what counts as significant, writing good issues
• Finding issues table: Differentiates good first issue (newcomers), help wanted (experienced contributors), and ready for work (maintainers)
• Claim guidance: Comment on issues before starting so we can assign them
• Pull Requests section: Scope expectations, what gets rejected, submitting guidelines
• Reorganized existing content under Development and Policies sections

Breaking Changes

None

Types of changes

• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/sdk@1311

commit: 762cc95

[pcarleton]

Suggested change

	- Features that might require spec changes (these need a [SEP](https://github.com/modelcontextprotocol/modelcontextprotocol) first)
	- Features that might require spec changes (these need a [SEP](https://modelcontextprotocol.io/community/sep-guidelines) first)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 762cc95

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[felixweinberger]

Thanks @pcarleton! Updated the SEP link in 762cc95.