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`.

cli/src/castle_cli/commands/create.py

@@ -14,6 +14,7 @@ from castle_cli.manifest import (
     HttpInternal,
     ManageSpec,
     ProgramSpec,
+    RunPath,
     RunPython,
     RunStatic,
     ServiceSpec,
@@ -109,7 +110,12 @@ def run_create(args: argparse.Namespace) -> int:
         behavior=behavior,
         build=build,
     )
-    if behavior == "frontend":
+    if behavior == "tool":
+        # A PATH-managed deployment: installed via `uv tool install`, no unit/route.
+        config.services[name] = ServiceSpec(
+            id=name, program=name, run=RunPath(runner="path")
+        )
+    elif behavior == "frontend":
         # A caddy-managed static service: no systemd unit, served from the build dir.
         config.services[name] = ServiceSpec(
             id=name,