Update Linear slug (#44424)

Rename Homebrew input for Linear from `linear-linear` to `linear` and
update slug paths accordingly. Update
ee/maintained-apps/outputs/apps.json and website routes to use
`linear/darwin` and the `/software-catalog/linear` route. Add
ee/maintained-apps/outputs/linear/darwin.json with version 1.28.13
metadata, installer/uninstall script refs and scripts, queries, and
sha256. This normalizes naming and exposes the Darwin package for
Linear.

ee/maintained-apps/inputs/homebrew/linear.json

@@ -1,8 +1,8 @@
 {
   "name": "Linear",
   "unique_identifier": "com.linear",
-  "token": "linear-linear",
+  "token": "linear",
   "installer_format": "zip",
-  "slug": "linear-linear/darwin",
+  "slug": "linear/darwin",
   "default_categories": ["Developer tools"]
 }

ee/maintained-apps/outputs/apps.json

@@ -1025,7 +1025,7 @@
     },
     {
       "name": "Linear",
-      "slug": "linear-linear/darwin",
+      "slug": "linear/darwin",
       "platform": "darwin",
       "unique_identifier": "com.linear",
       "description": "Linear is an app to manage software development and track bugs."