[T4] Reconnect budget reset + exhaustion surfacing

[dennisonbertram]

[parent] #1339

Problem

Reconnect attempt counter never resets on successful events → permanently dead streams (model.go ~4883).

Outcome

Reset attempts when connection delivers events; user-visible notice on exhaustion.

Acceptance criteria

• Simulated flaky stream survives >5 drops over session lifetime.

Test-first plan

Flaky-stream survival test (expected red).

Impact analysis

TUI-only.