Add a pluggable server extension API with MCP Apps #3133

Job	Run time
checks / docs	38s
checks / pre-commit	48s
checks / readme-snippets	12s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 14s
checks / test (3.11, lowest-direct, windows-latest)	1m 46s
checks / test (3.14, lowest-direct, windows-latest)	1m 33s
checks / test (3.11, locked, windows-latest)	1m 48s
checks / test (3.13, lowest-direct, windows-latest)	1m 42s
checks / test (3.10, locked, windows-latest)	1m 48s
checks / test (3.12, locked, ubuntu-latest)	1m 28s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 16s
checks / test (3.13, locked, windows-latest)	1m 39s
checks / test (3.12, lowest-direct, windows-latest)	1m 42s
checks / test (3.10, lowest-direct, windows-latest)	1m 35s
checks / test (3.11, lowest-direct, ubuntu-latest)	58s
checks / test (3.11, locked, ubuntu-latest)	1m 3s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.10, locked, ubuntu-latest)	1m 15s
checks / test (3.13, locked, ubuntu-latest)	1m 8s
checks / test (3.14, locked, ubuntu-latest)	2m 15s
checks / test (3.12, locked, windows-latest)	1m 31s
checks / test (3.14, locked, windows-latest)	2m 31s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 15s
all-green	4s
	32m 11s

Provide feedback