refactor skills registries and add GitHub-backed skill discovery (#2442)

* refactor skills registries and add GitHub-backed skill discovery

* fix ci

* fix command error

* fix default skills install registry behavior

* fix github registry URL parsing and versioned skill links

* fix skills registry config compatibility and URL installs

* * fix lint

* fix deprecated github base url compatibility

* fix skills registry yaml and github default branch handling

* fix github skills registry fallback and install metadata

* fix cli skills install origin metadata

* fix clawhub registry env compatibility

* fix skills registry config merge compatibility

* fix skill install metadata consistency and onboard template copy

* fix yaml overrides for default skills registries

* fix install_skill registry metadata normalization

* fix github skill URL parsing for slash branch names

* fix skills registry install/search validation and github URLs

* fix github skill URL host validation

* fix install_skill validation for invalid registry archives

* fix redundant skills registry names in saved config

* fix github blob skill URL installs and metadata links

* fix github registry URL scheme validation

* fix v0 skills migration preserving github registry defaults

* fix github blob skill install directory resolution

* fix install_skill rollback on origin metadata write failure

* fix github skill URL validation and registry JSON merging

* fix github registry target resolution and metadata links

* fix install_skill force reinstall rollback

* fix skills config compatibility and legacy security overlays

* fix ci

config/config.example.json

@@ -382,9 +382,16 @@
           "timeout": 0,
           "max_zip_size": 0,
           "max_response_size": 0
+        },
+        "github": {
+          "enabled": true,
+          "base_url": "https://github.com",
+          "auth_token": "",
+          "proxy": "http://127.0.0.1:7891"
         }
       },
       "github": {
+        "base_url": "https://github.com",
         "proxy": "http://127.0.0.1:7891",
         "token": ""
       },