[client] Implement MCP OAuth scope selection and step-up authorization #2874

Job	Run time
checks / readme-snippets	10s
checks / pre-commit	27s
checks / test (3.10, highest, ubuntu-latest)	33s
checks / test (3.10, lowest-direct, ubuntu-latest)	37s
checks / test (3.11, lowest-direct, windows-latest)	1m 23s
checks / test (3.10, highest, windows-latest)	1m 23s
checks / test (3.10, lowest-direct, windows-latest)	1m 21s
checks / test (3.11, highest, ubuntu-latest)	37s
checks / test (3.13, lowest-direct, ubuntu-latest)	34s
checks / test (3.11, highest, windows-latest)	1m 32s
checks / test (3.12, lowest-direct, windows-latest)	1m 48s
checks / test (3.13, highest, windows-latest)	1m 19s
checks / test (3.13, highest, ubuntu-latest)	36s
checks / test (3.11, lowest-direct, ubuntu-latest)	36s
checks / test (3.13, lowest-direct, windows-latest)	1m 27s
checks / test (3.12, highest, windows-latest)	1m 23s
checks / test (3.12, highest, ubuntu-latest)	31s
checks / test (3.12, lowest-direct, ubuntu-latest)	31s
	16m 48s

Provide feedback