Add a pluggable server extension API with MCP Apps #3138

Job	Run time
checks / readme-snippets	13s
checks / docs	43s
checks / pre-commit	51s
checks / test (3.13, lowest-direct, windows-latest)	1m 48s
checks / test (3.14, lowest-direct, windows-latest)	1m 50s
checks / test (3.14, locked, windows-latest)	2m 44s
checks / test (3.10, lowest-direct, windows-latest)	1m 51s
checks / test (3.10, locked, ubuntu-latest)	1m 13s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 12s
checks / test (3.12, locked, windows-latest)	1m 33s
checks / test (3.10, locked, windows-latest)	1m 49s
checks / test (3.11, lowest-direct, windows-latest)	1m 42s
checks / test (3.14, locked, ubuntu-latest)	2m 8s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.11, locked, ubuntu-latest)	1m 7s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 12s
checks / test (3.13, locked, windows-latest)	1m 39s
checks / test (3.12, lowest-direct, windows-latest)	1m 45s
checks / test (3.11, locked, windows-latest)	1m 37s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 21s
checks / test (3.12, locked, ubuntu-latest)	1m 33s
checks / test (3.13, locked, ubuntu-latest)	1m 5s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 10s
all-green	3s
	33m 11s

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