#11: termination: fix single rank case

[lifflander]

Fixes #11

[Copilot]

Pull request overview

This PR addresses issue #5 by adding special handling for the single rank (size=1) case in the termination detection algorithm. The termination detector uses a tree-based approach that doesn't work correctly when only one MPI rank exists, requiring specialized logic to progress the state machine.

Key changes:

• Extracted child completion checking into a new checkAllChildrenComplete() method
• Added singleRank() helper method and special case handling in sendControlToChildren() and wave restart logic
• Updated printf format specifiers from %lld to %" PRIu64 " for portable uint64_t printing

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/vt-lb/comm/MPI/termination.h	Adds new method declarations checkAllChildrenComplete() and singleRank() to support single rank termination detection
src/vt-lb/comm/MPI/termination.cc	Implements single rank handling logic, refactors completion checking, and fixes printf format specifiers for uint64_t
src/vt-lb/comm/MPI/comm_mpi.h	Adds single rank state machine progression in poll loop and initialization logic for rank 0

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[Copilot]

Missing closing underscore in format string: global_recv1_= should be global_recv1= to match the variable name pattern in the output (the other variables don't have trailing underscores in the format string).

Suggested change

	printf("Rank %d: received response: sent=%" PRIu64 ", recv=%" PRIu64 ", global_sent1=%" PRIu64 ", global_recv1=%" PRIu64 " waiting_children=%d\n",
	printf("Rank %d: received response: sent=%" PRIu64 ", recv=%" PRIu64 ", global_sent1=%" PRIu64 ", global_recv1_=%" PRIu64 " waiting_children=%d\n",

[nlslatt]

Looks good to me and fixes my problem.