fix(skills): correct invalid install kinds in xurl and github [AI] (#102158)

* fix(xurl): use install kind "node" instead of invalid "npm" [AI]

The xurl skill's second installer declares kind "npm", which is not a
valid install kind. The installer switches on spec.kind with cases for
brew/node/go/uv/download and a default of "unsupported installer", so the
entry is dropped -- `openclaw skills info xurl` only offers the brew
option, leaving no install path on machines without Homebrew.

npm-backed installs use kind "node" (which honors
skills.install.nodeManager, default npm). Only kind is changed;
id/package/bins are left as-is.

Verified against openclaw 2026.6.11 in a container:

  before (kind: npm):  Install options: → Install xurl (brew)
  after  (kind: node): Install options: → Install @xdevplatform/xurl (npm)

* fix(github): drop non-functional "apt" install entry [AI]

The github skill's second installer declares kind "apt", which is not a
supported install kind (installer switch handles brew/node/go/uv/download
+ default "unsupported installer"). openclaw silently drops it -- `skills
info github` only ever surfaces the brew option -- so the entry is dead,
misleading metadata rather than a working Linux path.

The remaining brew installer is cross-platform (Homebrew runs on Linux),
so removing the dead entry loses no working path. Improving install paths
for Linux users without Homebrew is tracked separately in #57555
(needs-product-decision).

skills/github/SKILL.md

@@ -16,13 +16,6 @@ metadata:
               "bins": ["gh"],
               "label": "Install GitHub CLI (brew)",
             },
-            {
-              "id": "apt",
-              "kind": "apt",
-              "package": "gh",
-              "bins": ["gh"],
-              "label": "Install GitHub CLI (apt)",
-            },
           ],
       },
   }

skills/xurl/SKILL.md

@@ -18,7 +18,7 @@ metadata:
             },
             {
               "id": "npm",
-              "kind": "npm",
+              "kind": "node",
               "package": "@xdevplatform/xurl",
               "bins": ["xurl"],
               "label": "Install xurl (npm)",