chore: drop github adapter set per WAWQAQ directive

WAWQAQ (#opencli-pr-review): "我们不需要GitHub的adapter，因为已经有GH了"

Removes the 5 github commands + utils + docs added in 664ed1a
(github/user, github/repo, github/search-repos, github/releases,
github/user-repos). The remaining 8 read commands across 5 sites
(arxiv author, stackoverflow user/tag, coingecko coin/trending,
wikipedia page, hf models/datasets) are unaffected.

Audit gates re-checked:
- check:typed-error-lint: 196/196 (baseline unchanged)
- check:silent-column-drop: 103/103 (baseline unchanged)
- doc-coverage: 112/112 (one less site documented)
- advise:listing-id-pairing: 12 advisory (unchanged)

Author: jackwener

cli-manifest.json

@@ -8607,223 +8607,6 @@
     "modulePath": "gitee/user.js",
     "sourceFile": "gitee/user.js"
   },
-  {
-    "site": "github",
-    "name": "releases",
-    "description": "List a public repository's releases (newest first).",
-    "access": "read",
-    "domain": "github.com",
-    "strategy": "public",
-    "browser": false,
-    "args": [
-      {
-        "name": "repo",
-        "type": "string",
-        "required": true,
-        "positional": true,
-        "help": "owner/repo (e.g. nodejs/node)"
-      },
-      {
-        "name": "limit",
-        "type": "int",
-        "default": 20,
-        "required": false,
-        "help": "Max releases to return (max 100; one API page)."
-      }
-    ],
-    "columns": [
-      "tagName",
-      "name",
-      "publishedAt",
-      "prerelease",
-      "draft",
-      "author",
-      "url"
-    ],
-    "type": "js",
-    "modulePath": "github/releases.js",
-    "sourceFile": "github/releases.js"
-  },
-  {
-    "site": "github",
-    "name": "repo",
-    "description": "Public GitHub repository metadata (stars, forks, language, license, dates).",
-    "access": "read",
-    "domain": "github.com",
-    "strategy": "public",
-    "browser": false,
-    "args": [
-      {
-        "name": "repo",
-        "type": "string",
-        "required": true,
-        "positional": true,
-        "help": "owner/repo (e.g. facebook/react)"
-      }
-    ],
-    "columns": [
-      "fullName",
-      "description",
-      "language",
-      "stars",
-      "forks",
-      "openIssues",
-      "watchers",
-      "license",
-      "defaultBranch",
-      "archived",
-      "fork",
-      "createdAt",
-      "updatedAt",
-      "pushedAt",
-      "url"
-    ],
-    "type": "js",
-    "modulePath": "github/repo.js",
-    "sourceFile": "github/repo.js"
-  },
-  {
-    "site": "github",
-    "name": "search-repos",
-    "description": "Search public repositories on GitHub.",
-    "access": "read",
-    "domain": "github.com",
-    "strategy": "public",
-    "browser": false,
-    "args": [
-      {
-        "name": "query",
-        "type": "string",
-        "required": true,
-        "positional": true,
-        "help": "Search query (supports GitHub search syntax e.g. \"react language:typescript\")"
-      },
-      {
-        "name": "sort",
-        "type": "string",
-        "default": "stars",
-        "required": false,
-        "help": "Sort key: stars, forks, updated, help-wanted-issues"
-      },
-      {
-        "name": "order",
-        "type": "string",
-        "default": "desc",
-        "required": false,
-        "help": "Order: desc, asc"
-      },
-      {
-        "name": "limit",
-        "type": "int",
-        "default": 20,
-        "required": false,
-        "help": "Max repos to return (max 100; one API page)."
-      }
-    ],
-    "columns": [
-      "fullName",
-      "description",
-      "language",
-      "stars",
-      "forks",
-      "updatedAt",
-      "url"
-    ],
-    "type": "js",
-    "modulePath": "github/search-repos.js",
-    "sourceFile": "github/search-repos.js"
-  },
-  {
-    "site": "github",
-    "name": "user",
-    "description": "Public GitHub user profile (login, bio, followers, repos count, etc.)",
-    "access": "read",
-    "domain": "github.com",
-    "strategy": "public",
-    "browser": false,
-    "args": [
-      {
-        "name": "username",
-        "type": "string",
-        "required": true,
-        "positional": true,
-        "help": "GitHub login (with or without leading @)"
-      }
-    ],
-    "columns": [
-      "login",
-      "name",
-      "bio",
-      "company",
-      "location",
-      "blog",
-      "followers",
-      "following",
-      "publicRepos",
-      "publicGists",
-      "createdAt",
-      "updatedAt",
-      "url"
-    ],
-    "type": "js",
-    "modulePath": "github/user.js",
-    "sourceFile": "github/user.js"
-  },
-  {
-    "site": "github",
-    "name": "user-repos",
-    "description": "List public repositories owned by a GitHub user.",
-    "access": "read",
-    "domain": "github.com",
-    "strategy": "public",
-    "browser": false,
-    "args": [
-      {
-        "name": "username",
-        "type": "string",
-        "required": true,
-        "positional": true,
-        "help": "GitHub login"
-      },
-      {
-        "name": "sort",
-        "type": "string",
-        "default": "updated",
-        "required": false,
-        "help": "Sort key: updated, created, pushed, full_name"
-      },
-      {
-        "name": "type",
-        "type": "string",
-        "default": "owner",
-        "required": false,
-        "help": "Filter: all, owner, member"
-      },
-      {
-        "name": "limit",
-        "type": "int",
-        "default": 30,
-        "required": false,
-        "help": "Max repos to return (max 100; one API page)."
-      }
-    ],
-    "columns": [
-      "name",
-      "fullName",
-      "description",
-      "language",
-      "stars",
-      "forks",
-      "archived",
-      "fork",
-      "updatedAt",
-      "pushedAt",
-      "url"
-    ],
-    "type": "js",
-    "modulePath": "github/user-repos.js",
-    "sourceFile": "github/user-repos.js"
-  },
   {
     "site": "google",
     "name": "news",