dark apps — a daemon / foreground / ui launch model

[StachuDotNet]

The one surface that lists, installs, and runs Apps — covering both background daemons and interactive UI apps, so the same dark apps manages the sync daemon, a print-md run, and the outliner TUI alike. An App is a package VALUE, so the manifest syncs like any other value.

The thin manifest + the three kinds

type AppKind = | Daemon | Foreground | Ui
type App =
  { name: String
    entrypoint: String          // Daemon: the loop fn (detached); Foreground: `dark run` target; Ui: the TUI fn
    description: String
    kind: AppKind
    spawnAllowList: List<String> }   // executables `apps install` grants as a Cli(spawn:…) capability

• Daemon — backgrounded long-runner; start/stop/status/logs manage it via a pidfile (sync daemon, heartbeat). Detached, survives CLI exit.
• Foreground — a normal dark run that finishes (print-md).
• Ui — a full-screen MVU TUI, attached until you quit (the outliner).

$ dark apps                          # the registry, at a glance
print-md   foreground   Render a markdown file to PDF and print it
heartbeat  daemon       A demo daemon: log a heartbeat every interval
outliner   ui           Interactive tree outliner (full-screen TUI)

$ dark apps start heartbeat          # detached; managed by pidfile
heartbeat running (pid 48213)
$ dark apps status heartbeat
heartbeat: running (pid 48213)

Install surface

apps install writes a one-line shell shim (~/.darklang/bin/<app> → dark run <entrypoint>) and grants the app's spawnAllowList as Cli(spawn: …). One dir on PATH, so uninstall is one file.

Tests

testfiles/execution/pre-s-and-s/apps.dark — 6/6: kindTag (×3), aliasPath, spawnGrantSummary (empty / non-empty). (findByName reads the all package-VALUE registry, which the .dark test harness can't resolve, so it's exercised via dark apps list at the CLI.) Build + reload clean.

Deferred

Type-discovery of Apps via the synced value index (this PR lists a static all); dark apps fork (later). Files: apps.dark, apps-daemon.dark, apps-examples.dark, …/cli/commands/apps.dark, core.dark, the testfile.