[Docs] Complete Sundial demo app tabs (Latency Dashboard, Protocol Comparison, Diagnostics)

[leogdion]

The Sundial example app's README (Examples/Sundial/README.md) advertises four tabs (Latency Dashboard, Protocol Comparison, Live Diagnostics) as implemented, but 6 of the 8 tab views are Text("Coming soon") stubs across both demo variants:

SundialDemoCombine

• Sources/SundialDemoCombine/App/LatencyDashboardView.swift:46
• Sources/SundialDemoCombine/App/ProtocolComparisonView.swift:46
• Sources/SundialDemoCombine/App/DiagnosticsView.swift:46

SundialDemoStream

• Sources/SundialDemoStream/App/StreamLatencyDashboardView.swift:46
• Sources/SundialDemoStream/App/StreamProtocolComparisonView.swift:46
• Sources/SundialDemoStream/App/StreamDiagnosticsView.swift:46

This work was previously tracked in IMPLEMENTATION_PLAN.md (Phases 3–5), which PR #91 removes. Opening this issue so the remaining demo work stays tracked after those session notes are deleted.

Tasks:

• Implement the Latency Dashboard tab (both variants)
• Implement the Protocol Comparison tab (both variants)
• Implement the Live Diagnostics tab (both variants)
• Or, if deferred, soften the README Features section so it doesn't claim these are implemented

Surfaced by the Claude Code review on #91.