runtime: fold venue adapters into the restart and poison sweeps

[mfw78]

Fold venue adapters into the restart and poison-recovery sweeps and expose an adapters_alive liveness signal. Adapters currently boot once and install but are not in the sweeps (supervisor.rs:61-66), so a trapped adapter stays dead until the process restarts and the router only projects the trap to an internal-error.

Why

Because adapters are outside the recovery sweeps, a strategy cannot tell an unknown venue (never installed) from a venue that is temporarily dead (trapped but recoverable), and a trapped adapter never comes back on its own. Folding adapters into the sweeps recovers them automatically, and a liveness signal lets strategies distinguish the two cases. This falls out naturally from extracting the generic supervised-component primitive from AdapterActor. Part of milestone M2: Generic venue-agnostic host. Blocked by: Extract a generic supervised-component primitive from AdapterActor. See docs/design/videre-split-plan.md and docs/design/issue-milestone-plan.md.

Scope

• Fold venue adapters, as the generalized provider/component kind, into the restart and poison-recovery sweeps.
• Expose adapters_alive or an equivalent liveness signal.
• Distinguish unknown-venue from venue-temporarily-dead.

Done when

• Trapped adapters are swept and restarted.
• A liveness signal distinguishes unknown-venue from venue-temporarily-dead.
• A trap-to-recovery test is present.

[mfw78]

Landed via #445 (squash-merged into dev/m1). Closing manually since the merge target is not the default branch.