ctx.elicit() throws an exception (not CancelledElicitation) when the
MCP client doesn't implement the elicitation/create JSON-RPC method.
Wrap the call in try/except to treat protocol-level rejection the
same as CancelledElicitation. Found during live testing with Claude
Code CLI which doesn't support MCP elicitation yet.
Three-pillar fix from Hamilton review:
Code quality — validate_signature() for D-Bus spec compliance,
MCDBUS_TIMEOUT env var, replace 13 error-as-success returns with
ToolError, monotonic clock deadline on tree walks, sanitize D-Bus
error messages, fix resource connection leak via module-level
BusManager, hasattr guards in conftest.
Elicitation — ctx.elicit() confirmation for system bus call_method
and all set_property calls, graceful degradation when client lacks
elicitation support, MCDBUS_REQUIRE_ELICITATION for hard-fail mode.
Permission docs — four-layer guide (systemd sandboxing, dbus-broker
policy, polkit rules, xdg-dbus-proxy) with ready-to-deploy example
configs validated against xmllint, bash -n, and systemd-analyze.
