feat(fastmcp): add include_in_context parameter to resource decorator

[rinaldofesta]

Summary

Adds a user-friendly include_in_context boolean parameter to the @resource decorator that automatically sets priority=1.0 in annotations. This simplifies marking resources for context inclusion without requiring users to manually create and manage Annotations objects.

Closes #1657

Motivation

Currently, users must create an Annotations object to set resource priority for context inclusion:

@mcp.resource("resource://data", annotations=Annotations(priority=1.0))
def get_data():
    return "important data"

This PR introduces a simpler API:

@mcp.resource("resource://data", include_in_context=True)
def get_data():
    return "important data"

Implementation

• Parameter behavior: When include_in_context=True, automatically sets priority=1.0
• Override logic: Always overrides explicit priority values when enabled
• Field preservation: Preserves other annotation fields like audience
• Broad support: Works with both regular and template resources, sync and async functions

Changes

• Modified FastMCP.resource() decorator to accept include_in_context parameter
• Added logic to create/update annotations with priority=1.0 when enabled
• Updated docstring with parameter documentation
• Added 6 comprehensive tests covering various scenarios

Test Plan

• include_in_context=True sets priority to 1.0
• include_in_context=False doesn't affect annotations
• Overrides explicit priority values
• Preserves audience annotations
• Works with template resources
• Works with async functions
• All existing annotation tests still pass (backward compatibility)

[jlowin]

I responded on #1657 (not sure where the discussion should accrue) but I see this as introducing a new problem (two kwargs for one outcome, one of which has misleading effect) rather than solving an existing one.

[maxisbey]

Thanks for the contribution! Unfortunately I'll be closing the PR as per #1657 (comment)

Basically, this is already supported in both the spec and framework as is, I don't think we need to have it hardcoded as an arg in the decorators.