Phase 25: templates as stack folders (0.31.0)

Templates are now stack-shaped folders (compose.yaml + .env.example +
template.json) instead of DB rows + manifest.json + {{VAR}} rendering.
Pull copies the folder into a new stack; custom templates persist under
DATA_DIR/templates. Adds POST /api/templates/from-stack and a one-time
startup migration for pre-0.31 DB templates (drops the template table).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/routers/templates.py

@@ -1,4 +1,8 @@
-"""Template library endpoints."""
+"""Template library endpoints.
+
+Templates are stack-shaped folders on disk. Listing reads them; "instantiate"
+(pull) copies the whole folder into a new stack, which is then editable.
+"""
 from __future__ import annotations
 
 import os
@@ -10,7 +14,11 @@ from auth import get_current_user, require_admin
 from database import get_session
 from models.agent import Agent
 from models.stack import Stack
-from models.template import TemplateInstantiateRequest, TemplateSaveRequest
+from models.template import (
+    TemplateFromStackRequest,
+    TemplateInstantiateRequest,
+    TemplateSaveRequest,
+)
 from models.user import User
 from services import agent_service, audit_service, compose_service, template_service
 from services.agent_service import AgentError
@@ -24,19 +32,17 @@ def _ip(request: Request) -> str:
 
 @router.get("")
 def list_templates(
-    session: Session = Depends(get_session),
     _user: User = Depends(get_current_user),
 ) -> list[dict]:
-    return template_service.list_templates(session)
+    return template_service.list_templates()
 
 
 @router.get("/{template_id}")
 def get_template(
     template_id: str,
-    session: Session = Depends(get_session),
     _user: User = Depends(get_current_user),
 ) -> dict:
-    tpl = template_service.get_template(session, template_id)
+    tpl = template_service.get_template(template_id)
     if not tpl:
         raise HTTPException(status_code=404, detail="Template not found")
     return tpl
@@ -49,13 +55,32 @@ def save_template(
     session: Session = Depends(get_session),
     user: User = Depends(require_admin),
 ) -> dict:
-    tpl = template_service.save_custom(
-        session, body.name, body.yaml, body.description or "", body.tags
+    slug = template_service.save_custom(
+        body.name, body.compose, body.env, body.description or "", body.tags, body.gpu
     )
     audit_service.record(
-        session, user=user.username, action="template.save", target=tpl.slug, ip=_ip(request)
+        session, user=user.username, action="template.save", target=slug, ip=_ip(request)
     )
-    return {"id": f"custom:{tpl.slug}", "name": tpl.name}
+    return {"id": f"custom:{slug}", "name": body.name}
+
+
+@router.post("/from-stack")
+def save_from_stack(
+    body: TemplateFromStackRequest,
+    request: Request,
+    session: Session = Depends(get_session),
+    user: User = Depends(require_admin),
+) -> dict:
+    if not session.get(Stack, body.stack_id) and not os.path.isdir(
+        compose_service.stack_dir(body.stack_id)
+    ):
+        raise HTTPException(status_code=404, detail=f"Stack '{body.stack_id}' not found")
+    slug = template_service.save_from_stack(body.stack_id, body.name, body.description or "")
+    audit_service.record(
+        session, user=user.username, action="template.save",
+        target=slug, detail=body.stack_id, ip=_ip(request),
+    )
+    return {"id": f"custom:{slug}", "name": body.name}
 
 
 @router.delete("/custom/{slug}")
@@ -65,7 +90,7 @@ def delete_template(
     session: Session = Depends(get_session),
     user: User = Depends(require_admin),
 ) -> dict:
-    if not template_service.delete_custom(session, slug):
+    if not template_service.delete_custom(slug):
         raise HTTPException(status_code=404, detail="Custom template not found")
     audit_service.record(
         session, user=user.username, action="template.delete", target=slug, ip=_ip(request)
@@ -81,12 +106,11 @@ async def instantiate(
     session: Session = Depends(get_session),
     user: User = Depends(require_admin),
 ) -> dict:
-    tpl = template_service.get_template(session, template_id)
+    tpl = template_service.get_template(template_id)
     if not tpl:
         raise HTTPException(status_code=404, detail="Template not found")
 
-    rendered = template_service.render(tpl["yaml"], body.values)
-
+    # Remote host: agents don't share our filesystem, so ship compose + env.
     if body.agent_id is not None:
         agent = session.get(Agent, body.agent_id)
         if not agent:
@@ -94,7 +118,7 @@ async def instantiate(
         try:
             result = await agent_service.call(
                 session, agent, "POST", "/agent/stacks",
-                json={"name": body.name, "yaml": rendered, "env": None},
+                json={"name": body.name, "yaml": tpl["compose"], "env": tpl["env"] or None},
             )
         except AgentError as exc:
             raise HTTPException(
@@ -107,11 +131,18 @@ async def instantiate(
         )
         return {"id": result.get("id"), "name": body.name, "agent_id": agent.id}
 
+    # Local host: copy the whole template folder into a new stack.
     stack_id = compose_service.slugify(body.name)
     if session.get(Stack, stack_id) or os.path.isdir(compose_service.stack_dir(stack_id)):
         raise HTTPException(status_code=409, detail=f"Stack '{stack_id}' already exists")
 
-    compose_service.write_compose(stack_id, rendered)
+    try:
+        template_service.copy_into_stack(template_id, stack_id)
+    except FileExistsError:
+        raise HTTPException(status_code=409, detail=f"Stack '{stack_id}' already exists")
+    except FileNotFoundError:
+        raise HTTPException(status_code=404, detail="Template not found")
+
     stack = Stack(id=stack_id, name=body.name, description=tpl.get("description"))
     session.add(stack)
     session.commit()