Integrate the Commander adapter with master's headless rework (dsh -p now boots
through AppCLIEntry — the same cordis.yml composition as dsh web, web-observable
while it runs — via toFetchHandler(ctx.apiProxy)).
- headless.ts: keep master's AppCLIEntry-based body but take the adapter's
pre-parsed `task` (drop the re-added parseArgs). Old startHost path and the
now-deleted packages/host/runtime dependency are gone.
- remove the stale packages/host/runtime dir left on disk by master's deletion
(mirrors the earlier packages/ui/acp cleanup).
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