feat: Add Line plugin (#1630)

* feat: add LINE plugin (#1630) (thanks @plum-dawg)

* feat: complete LINE plugin (#1630) (thanks @plum-dawg)

* chore: drop line plugin node_modules (#1630) (thanks @plum-dawg)

* test: mock /context report in commands test (#1630) (thanks @plum-dawg)

* test: limit macOS CI workers to avoid OOM (#1630) (thanks @plum-dawg)

* test: reduce macOS CI vitest workers (#1630) (thanks @plum-dawg)

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

extensions/line/clawdbot.plugin.json

@@ -0,0 +1,11 @@
+{
+  "id": "line",
+  "channels": [
+    "line"
+  ],
+  "configSchema": {
+    "type": "object",
+    "additionalProperties": false,
+    "properties": {}
+  }
+}