feat: Add marketplace source filtering and plugin share context (#21419)

Adds marketplaceKinds to plugin/list for local, workspace-directory, and
shared-with-me; omitted params keep default local plus gated global
behavior, while explicit kinds are exact.

Exposes shareContext on plugin summaries from local share mappings and
remote workspace/shared responses, including remotePluginId and nullable
creator metadata.

Adds shared-with-me listing through /ps/plugins/workspace/shared,
renames the workspace remote namespace to workspace-directory, and keeps
direct remote read/share/install/update/delete paths gated by plugins
rather than remote_plugin.

codex-rs/app-server-protocol/schema/json/ClientRequest.json

@@ -2144,6 +2144,14 @@
       ],
       "type": "object"
     },
+    "PluginListMarketplaceKind": {
+      "enum": [
+        "local",
+        "workspace-directory",
+        "shared-with-me"
+      ],
+      "type": "string"
+    },
     "PluginListParams": {
       "properties": {
         "cwds": {
@@ -2155,6 +2163,16 @@
             "array",
             "null"
           ]
+        },
+        "marketplaceKinds": {
+          "description": "Optional marketplace kind filter. When omitted, only local marketplaces are queried, plus the default remote catalog when enabled by feature flag.",
+          "items": {
+            "$ref": "#/definitions/PluginListMarketplaceKind"
+          },
+          "type": [
+            "array",
+            "null"
+          ]
         }
       },
       "type": "object"