Add a pluggable server extension API with MCP Apps #3162

Job	Run time
checks / readme-snippets	11s
checks / docs	39s
checks / pre-commit	45s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 13s
checks / test (3.10, locked, windows-latest)	1m 59s
checks / test (3.11, locked, ubuntu-latest)	1m 12s
checks / test (3.10, lowest-direct, windows-latest)	1m 33s
checks / test (3.11, lowest-direct, windows-latest)	1m 52s
checks / test (3.12, locked, ubuntu-latest)	1m 25s
checks / test (3.12, lowest-direct, windows-latest)	1m 29s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 19s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 15s
checks / test (3.12, locked, windows-latest)	1m 49s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 11s
checks / test (3.11, locked, windows-latest)	1m 25s
checks / test (3.13, lowest-direct, windows-latest)	1m 36s
checks / test (3.13, locked, windows-latest)	1m 43s
checks / test (3.10, locked, ubuntu-latest)	1m 12s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 7s
checks / test (3.14, lowest-direct, windows-latest)	1m 36s
checks / test (3.14, locked, ubuntu-latest)	2m 10s
checks / test (3.14, locked, windows-latest)	2m 27s
checks / test (3.13, locked, ubuntu-latest)	1m 4s
all-green	4s
	32m 16s

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