plugins: a plugin's tasks are read where they live

the last piece of docs/plugin-capabilities.md. skills, affordances and
notification catalogues already loaded from each installed and enabled
plugin's own directory; tasks did not, so the transcribe plugin shipped a
task nothing could see — right-clicking an .m4a offered no Run Task at all.

it turned out to be one function rather than several. every path that runs
a task resolves it through getTaskByDirName and then reads implementation
off the record, so the sources go in there and in listTasks and a plugin's
task is runnable everywhere at once, identity unchanged: still a directory
name, still what pipeline_jobs stores.

the record carries `plugin` and that one field does the rest. updateTask
and deleteTask throw on it, DELETE /api/tasks/:name answers 409 naming the
plugin, and the capability screen shows whose it is instead of an edit and
a delete that cannot work. without the delete guard it was quietly a no-op:
rm -rf on a path in the owner's store that does not exist, then ok: true,
and the task still in the menu.

owner's store first, so a plugin cannot take over a name already in use.

getTaskByDirName now refuses a name containing a separator. it always
joined a caller-supplied string onto a path — from a websocket message and
a job row — and searching several roots is the moment that stops being one
directory nobody could escape.

capabilityRootsFrom is gone; it was dead. capabilitySources replaces it and
carries the provenance, with capabilityRoots the thin map over it that the
loaders that only want paths still use.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Officer-Session: 656f5c85-e49a-4f1f-b9f3-042a04b4d043

src/servers/api/tasks/tasks.ts

@@ -15,6 +15,7 @@ tasksRouter.get('/', async (ctx) => {
     category: row.category,
     triggers: (row.trigger as TriggerConfig[]) ?? [],
     mode: row.mode ?? 'agentic',
+    plugin: row.plugin,
   }));
 
   return ctx.json(tasks);
@@ -47,6 +48,7 @@ tasksRouter.get('/:name', async (ctx) => {
     config: task.config,
     version: task.version,
     filePath: task.filePath,
+    plugin: task.plugin,
   });
 });
 
@@ -74,6 +76,8 @@ tasksRouter.delete('/:name', async (ctx) => {
 
   const task = await getTaskByDirName(name);
   if (!task) return ctx.text('Not found', 404);
+  // A plugin's task is its own file in its own checkout. Uninstalling the plugin is how it goes away.
+  if (task.plugin) return ctx.text(`${name} belongs to the ${task.plugin} plugin — uninstall it instead`, 409);
 
   await deleteTask(task.dirName);
   return ctx.json({ ok: true });