feat(maestro): force-kill prompt in the web client

The kill button now sends the unforced DELETE immediately instead of
asking first. Only the daemon's guard refusal raises a prompt, and it is
a real dialog rather than confirm(), so it can offer the override the
daemon already implements.

The API error envelope is decoded into ApiRequestError, keeping the code
and the unsaved-work breakdown so the dialog names what is in the way.

web/src/routes.ts

@@ -18,6 +18,10 @@ export const EVENTS = "/api/events";
 /** Name of the query parameter `DIRS` and `GITROOT` both take. */
 export const PATH_QUERY = "path";
 
+/** Name of the query parameter `DELETE /api/sessions/:id` takes (#81):
+ * `force=true` overrides the kill refusal over a guarded worktree. */
+export const FORCE_QUERY = "force";
+
 /** Name of the query parameter `NAMES` takes. */
 export const COUNT_QUERY = "count";