The workspace-app and port preview tabs in the Coder Agents right panel
were previously gated behind a `devel` prerelease build check, which
can't be toggled in real deployments.
This replaces that check with a proper `agent-app-tabs` deployment
experiment, registered in `ExperimentsKnown`, so the feature can be
enabled via `CODER_EXPERIMENTS=agent-app-tabs` like any other
experiment. The frontend now reads
`experiments.includes("agent-app-tabs")` from the dashboard instead of
`getPrereleaseFlag(buildInfo) === "devel"`.
Depends on #26208