[T6] Lifecycle/memory batch

[dennisonbertram]

[parent] #1339
Five micro-fixes:

1. RunFailedMsg invokes cancelRun and nils bridge (model.go ~4197)
2. Bounded viewport maxHistory at construction (components/viewport/model.go ~19)
3. OSC52 via bubbletea sequencing + chunking (clipboard.go ~18)
4. url.PathEscape on sseEventsURL/dashboardControlCmd (api.go ~1428, dashboard.go ~127)
5. Delta handler run-identity guard (model.go ~4565)

Acceptance criteria

Unit tests for each micro-fix.

Impact analysis

TUI-only.