Add network debug surfaces and refresh telemetry docs

[MontrealAI]

Summary

• extend /debug/network and /debug/resources so operators receive window-aligned reachability timelines, per-transport dial summaries, and timestamped NRM/Connection Manager snapshots that mirror the dashboard tiles
• enhance the Telemetry SPA and stylesheet with per-transport success pills, reachability window indicators, and inline snapshot callouts driven by the new API payloads
• refresh the runbook and README with the Sprint E6 overlays, new Mermaid system diagram, and direct links to the updated operational guidance

Testing

• npm run test
• npm run test:frontend

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Codex Task