[codex] Add idle timeout and cancel running commands

[lobis]

Summary

• add a default one-hour interactive idle timeout with --idle-timeout / EOS_TUI_IDLE_TIMEOUT
• wire the Bubble Tea program and EOS client to a shared signal-aware run context
• cancel in-flight EOS/SSH commands when the client closes instead of waiting for command timeouts
• document the new option and cover idle/cancel behavior with tests

Why

On eospilot, abandoned interactive sessions can keep eos-tui refreshing EOS state indefinitely. Session logs showed long-lived runs, especially in high-frequency IO shaping views. This change gives normal interactive runs a bounded lifetime while still allowing intentional dashboard use with --idle-timeout=0.

Validation

• go test ./...
• go build ./...
• deployed and smoke-checked a local build on eospilot and lobis-eos-dev as v0.2.12+idlefix.20260520