Fix kernel CpuContext validation and EndUserRuntime service error mapping

[ARARAT33]

Updates ALLOWED_RFLAGS in kernel/src/process/context.rs to allow CPU reserved bit 1 (0x2), maps RuntimeError into EndUserRuntimeError::Core in start_service, permits ServiceState::Failed transitions in fail_service, and fixes test assertions to achieve 100% test suite passing across all workspace crates.

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PR created automatically by Jules for task 16479094871560718587 started by @ARARAT33

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