Add a pluggable server extension API with MCP Apps #3136

Job	Run time
checks / pre-commit	47s
checks / readme-snippets	12s
checks / docs	38s
checks / test (3.12, lowest-direct, windows-latest)	1m 44s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 12s
checks / test (3.12, locked, ubuntu-latest)	1m 28s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 19s
checks / test (3.10, locked, windows-latest)	1m 42s
checks / test (3.13, lowest-direct, windows-latest)	1m 56s
checks / test (3.14, locked, ubuntu-latest)	2m 9s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.12, locked, windows-latest)	1m 44s
checks / test (3.14, lowest-direct, windows-latest)	1m 34s
checks / test (3.13, locked, windows-latest)	1m 52s
checks / test (3.14, locked, windows-latest)	2m 54s
checks / test (3.13, locked, ubuntu-latest)	1m 11s
checks / test (3.11, locked, ubuntu-latest)	1m 5s
checks / test (3.11, lowest-direct, ubuntu-latest)	59s
checks / test (3.10, locked, ubuntu-latest)	1m 17s
checks / test (3.11, locked, windows-latest)	1m 56s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 15s
checks / test (3.11, lowest-direct, windows-latest)	1m 45s
checks / test (3.10, lowest-direct, windows-latest)	1m 21s
all-green	3s
	33m 8s

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