docs: add Mermaid diagrams to improve visual documentation
Enhance documentation with six Mermaid diagrams to better explain
complex system implementations:
- Adaptive polling lifecycle flowchart showing enqueue→execute→feedback
cycle with scheduler, priority queue, and worker interactions
- Circuit breaker state machine diagram illustrating Closed↔Open↔Half-open
transitions with triggers and recovery paths
- Temperature proxy architecture diagram highlighting trust boundaries,
security controls, and data flow between host/container/cluster
- Sensor proxy request flow sequence diagram showing auth, rate limiting,
validation, and SSH execution pipeline
- Alert webhook pipeline flowchart detailing template resolution, URL
rendering, HTTP dispatch, and retry logic
- Script library workflow diagram illustrating dev→test→bundle→distribute
lifecycle emphasizing modular design
These visualizations make it easier for operators and contributors to
understand Pulse's sophisticated architectural patterns.
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