Add app runner for backend and discord stack

pm/tasks-v2.org

@@ -242,7 +242,56 @@ delete or retire legacy bot behaviors that no longer fit once the backend split
 - cleanup updated user-facing deployment artifacts to match the v2 naming and architecture, including `DISCORD_BOT_TOKEN` and removal of `users.json` references
 - archived planning docs were intentionally left untouched: `pm/tasks.org` is historical and `pm/notes.org` is personal working notes
 
-* [ ] 2.0.4: fix automation and build pipeline (3)
+* [ ] 2.0.4: make youdis.py app runner for backend + adapters (3)
+Build a simple Python orchestration layer in youdis.py so the standard app stack can be launched from one entrypoint while backend and adapters remain independently runnable for testing.
+
+** pm notes
+- keep components independently runnable
+- youdis.py as app-level orchestrator; let Docker just run python3 /app/youdis.py
+- no plugin discovery or hot-loading
+- Docker should package and launch the app, not decide internal process topology
+- preserve the ability to run backend or adapters directly for debugging
+- optimize for one obvious default run path
+
+** Acceptance Criteria
+1. define the default app startup path
+   - youdis.py launches the standard stack for v2
+   - backend and Discord adapter startup order is explicit
+   - shutdown behavior is coherent enough for local/dev use
+2. preserve modular run paths
+   - backend can still be run directly
+   - Discord adapter can still be run directly
+   - orchestration layer does not bury component-level testing
+3. keep orchestration simple
+   - no dynamic adapter discovery
+   - no hot reloading framework
+   - configured components are started explicitly
+4. document runtime ownership
+   - clarify what Python orchestrates vs what Docker orchestrates
+   - identify env vars or flags that control which components start
+   - leave room for future Zulip/XMPP adapters without redesigning the runner
+
+** evidence
+- commit:
+- tests:
+  1. `python3 -m py_compile ./youdis.py ./youdis/adapters/discord.py`
+  2. backend direct run still works: `python3 -m uvicorn youdis.main:app --host 127.0.0.1 --port 8000`
+  3. discord direct run still works: `python3 -m youdis.adapters.discord`
+  4. app runner backend-only smoke test: `YOUDIS_RUN_DISCORD=0 timeout 5s python3 ./youdis.py`
+  5. app runner default path: `python3 ./youdis.py`
+- date:
+
+** notes
+- `youdis.py` is now the default v2 app runner and starts the standard stack explicitly rather than dynamically discovering adapters
+- backend starts first and must pass a health check before the Discord adapter is launched
+- backend and Discord adapter remain directly runnable for debugging and tests
+- Docker is intended to invoke `python3 /app/youdis.py`; Python owns app orchestration while Docker owns packaging and runtime environment
+- runner flags currently include `YOUDIS_RUN_BACKEND`, `YOUDIS_RUN_DISCORD`, `YOUDIS_BACKEND_HOST`, and `YOUDIS_BACKEND_PORT`
+
+
+* ==== BACKLOG ====
+Tasks below this line are inactive and should not be touched.
+* [ ] 2.0.X: fix automation and build pipeline (3)
 repair and simplify the build/update/deploy path so it matches the new backend-plus-frontend structure
 ** pm notes
 - this should come after architecture and discord integration stabilize. no point polishing the pipeline for the wrong shape.
@@ -267,8 +316,6 @@ repair and simplify the build/update/deploy path so it matches the new backend-p
 
 ** notes
 
-* ==== BACKLOG ====
-Tasks below this line are inactive and should not be touched.
 * [ ] X.x.x: clean up discord adapter UI
 
 ** acceptance criteria