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`.

core/src/castle_core/manifest.py

@@ -89,9 +89,27 @@ class RunStatic(RunBase):
     root: str = "dist"  # served dir, relative to the program source
 
 
+class RunPath(RunBase):
+    """A CLI installed on the user's PATH via ``uv tool install`` — no process.
+
+    Like ``remote``/``static`` it has no systemd unit; its manager is **PATH**.
+    The referenced program is what gets installed; its lifecycle is
+    install/uninstall (which is what start/stop/enable/disable map to).
+    """
+
+    runner: Literal["path"]
+
+
 RunSpec = Annotated[
     Union[
-        RunCommand, RunPython, RunContainer, RunNode, RunCompose, RunRemote, RunStatic
+        RunCommand,
+        RunPython,
+        RunContainer,
+        RunNode,
+        RunCompose,
+        RunRemote,
+        RunStatic,
+        RunPath,
     ],
     Field(discriminator="runner"),
 ]