feat(mcpserver): let ToolError carry content for is_error results #3027

Job	Run time
checks / pre-commit	35s
checks / readme-snippets	17s
checks / test (3.14, lowest-direct, ubuntu-latest)	20s
checks / test (3.10, lowest-direct, windows-latest)	42s
checks / test (3.10, lowest-direct, ubuntu-latest)	16s
checks / test (3.13, locked, ubuntu-latest)	17s
checks / test (3.14, locked, ubuntu-latest)	1m 22s
checks / test (3.14, locked, windows-latest)	1m 47s
checks / test (3.10, locked, ubuntu-latest)	17s
checks / test (3.11, lowest-direct, ubuntu-latest)	19s
checks / test (3.12, locked, windows-latest)	38s
checks / test (3.12, locked, ubuntu-latest)	14s
checks / test (3.11, locked, windows-latest)	41s
checks / test (3.11, locked, ubuntu-latest)	15s
checks / test (3.12, lowest-direct, windows-latest)	46s
checks / test (3.12, lowest-direct, ubuntu-latest)	19s
checks / test (3.13, lowest-direct, windows-latest)	38s
checks / test (3.14, lowest-direct, windows-latest)	51s
checks / test (3.10, locked, windows-latest)	40s
checks / test (3.13, locked, windows-latest)	48s
checks / test (3.13, lowest-direct, ubuntu-latest)	20s
checks / test (3.11, lowest-direct, windows-latest)	40s
all-green	5s
	13m 7s

Provide feedback