feat: add remove_prompt() and remove_resource() for parity with remove_tool()

[goingforstudying-ctrl]

Summary

MCPServer exposes remove_tool(name) but has no equivalent for prompts or resources.
This was part of the original ask in #711, which was closed when remove_tool()
landed — but the resource and prompt sides were never addressed.

Changes

Primitive	add_*	remove_*
Tool	✅	✅ (existing)
Prompt	✅	✅ (new)
Resource	✅	✅ (new)
Resource Template	✅	✅ (new)

API Additions

• PromptManager.remove_prompt(name) — raises PromptError if not found
• ResourceManager.remove_resource(uri) — raises ResourceError if not found
• ResourceManager.remove_template(uri_template) — raises ResourceError if not found
• MCPServer.remove_prompt(name) — thin wrapper delegating to the manager
• MCPServer.remove_resource(uri) — thin wrapper delegating to the manager
• MCPServer.remove_resource_template(uri_template) — thin wrapper
• PromptError exception class in exceptions.py

Purely additive, no breaking changes.

Use Case

Multi-tenant / multi-instance deployments where the same server image serves
different clients. Users can now filter all primitives per-instance without
reaching into private internals.

Fixes #2331

[rgoldstein1989]

Thanks for picking this up! A couple of things I noticed:

Missing tests

The project requires 100% code coverage (fail_under = 100 in CI), and CONTRIBUTING.md states "Add tests for new functionality." This PR will fail CI without tests. For reference, the existing remove_tool() has tests in both test_tool_manager.py and test_server.py covering:

• Removing an existing item
• Removing a non-existent item (error path)
• Removing one item from multiple and verifying list_* results
• Calling/reading a removed item through the client (verifying the protocol-level error)

The same coverage would be needed for remove_prompt, remove_resource, and remove_resource_template.

remove_resource uri type

The uri parameter on ResourceManager.remove_resource() is typed as str, but resources are stored via str(resource.uri) where resource.uri can be AnyUrl. If a caller passes an AnyUrl object, the lookup will fail silently (no match in the dict) and raise ResourceError even though the resource exists.

The fix is to accept AnyUrl | str and normalize before lookup, matching how the rest of the manager handles URIs:

def remove_resource(self, uri: AnyUrl | str) -> None:
    uri_str = str(uri)
    if uri_str not in self._resources:
        raise ResourceError(f"Unknown resource: {uri}")
    del self._resources[uri_str]

get_resource() already does this same str(uri) normalization at the top of the method.

[goingforstudying-ctrl]

@rgoldstein1989 Thanks for the detailed review! I've addressed both issues:

1. Added comprehensive tests for all new functionality:

   • : existing, non-existent, multiple prompts, protocol-level error
   • : existing, non-existent, AnyUrl support, multiple resources, protocol-level error
   • : existing, non-existent, multiple templates

2. Fixed URI type: Now accepts and normalizes with before lookup, matching behavior.

All tests should now pass. Please take another look when you have time!