Add compose-metrics.ds (Layer 1): receives counter+clock+stats,
derives uptime/events/status, re-streams on /peer/metrics. This app
is BOTH a receiver and a source.
Add compose-master.ds (Layer 2): receives chained metrics from
Layer 1 + mood direct from Layer 0. Demonstrates multi-layer
signal composition with independent stream mixing.
Verified: Uptime: 51s, Total Events: 9 flowing through the full
three-layer chain to the master dashboard.
