Tools as PATH deployments; demote behavior from lifecycle logic

- manifest: RunPath (runner: path) — a CLI on PATH via `uv tool install`, manager
  = path, no unit/route (like remote/static).
- lifecycle/service: a path deployment's start/stop = install/uninstall (routed
  through activate/deactivate, which skip the reinstall when already on PATH).
  `castle service start/stop <tool>` and status now dispatch by manager; status
  shows the manager tag [systemd|caddy|path|none].
- config.tools() now derives from `runner: path` services, not the behavior label.
- castle-api: the "installed" flag derives from manager==path, not behavior==tool.
- create: a python-cli stack emits a `runner: path` service.

`behavior` no longer drives any runtime logic — it survives only as a display
label + `list --behavior` filter. Verified live: html2text uninstall→reinstall
round-trip via `castle service stop/start`.

castle-api/src/castle_api/routes.py

@@ -10,7 +10,7 @@ from fastapi import APIRouter, HTTPException, status
 
 from castle_core.config import SPECS_DIR
 from castle_core.generators.caddyfile import generate_caddyfile_from_registry
-from castle_core.manifest import ProgramSpec, JobSpec, ServiceSpec
+from castle_core.manifest import ProgramSpec, JobSpec, ServiceSpec, manager_for
 from castle_core.stacks import available_actions
 
 from castle_api.config import get_castle_root, get_registry
@@ -70,9 +70,9 @@ def _summary_from_deployed(name: str, deployed: object) -> DeploymentSummary:
             timer=has_timer,
         )
 
-    # Check if tool is installed on PATH
+    # A PATH-managed deployment (a tool) is "installed" when it's on PATH.
     installed: bool | None = None
-    if deployed.behavior == "tool":
+    if manager_for(deployed.runner) == "path":
         installed = shutil.which(name) is not None
 
     category = "job" if deployed.schedule else "service"