Reword the branching-model section of AGENTS.md: instead of banning @deprecated shims and backward-compat layers outright on main, state that removing or replacing an API must be intentional, and that adding a replacement API or @deprecated shim must likewise be a deliberate design choice rather than something bolted on by default.

Motivation and Context

The old wording read as an absolute rule, but sometimes a shim is the right call during the v2 rework — it just has to be a conscious decision. This also makes explicit that a breaking change still needs a docs/migration.md entry even when a compat shim softens it, and echoes that in the Breaking Changes section so it's visible to readers who jump straight there.

How Has This Been Tested?

Docs-only change; pre-commit (markdownlint) passes.

Breaking Changes

None.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• 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

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