Use C++17 concatenated namespaces, add [[nodiscard]] to query methods,
add missing direct includes, and use pass-by-value + std::move in
NullTelemetry constructor.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Instrument the consensus subsystem with OpenTelemetry spans covering
the full round lifecycle: round start, establish phase, proposal send,
ledger close, position updates, consensus check, accept, validation
send, and mode changes.
Key design choices adapted from the original Phase 4 implementation
to the new SpanGuard factory pattern introduced in Phase 3:
- Add SpanGuard::hashSpan() for category-gated hash-derived trace IDs
(consensus round spans share trace_id across validators via ledger hash)
- Add SpanGuard::addEvent() overload with key-value attribute pairs
(used for dispute.resolve events during position updates)
- Add ConsensusSpanNames.h with compile-time span name constants
following the colocated *SpanNames.h pattern from Phase 3
- Add consensusTraceStrategy config option ("deterministic"/"attribute")
for cross-node trace correlation strategy selection
- Use SpanGuard::linkedSpan() for follows-from relationships between
consecutive rounds and cross-thread validation spans
- Use SpanGuard::captureContext() for thread-safe context propagation
from consensus thread to jtACCEPT worker thread
Spans produced: consensus.round, consensus.proposal.send,
consensus.ledger_close, consensus.establish, consensus.update_positions,
consensus.check, consensus.accept, consensus.accept.apply,
consensus.validation.send, consensus.mode_change
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
