ci: bump mcp-publisher to v1.7.9 to fix OIDC audience mismatch

v1.4.0 requested the github-oidc token with audience "mcp-registry",
but the registry now requires "https://registry.modelcontextprotocol.io"
(security fix CVE-2026-44428), causing 401 on login. v1.7.6+ sends the
correct audience.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: tianzhou

.github/workflows/mcp-publish.yml

@@ -24,7 +24,7 @@ jobs:
 
       - name: Install MCP Publisher
         run: |
-          curl -L "https://github.com/modelcontextprotocol/registry/releases/download/v1.4.0/mcp-publisher_$(uname -s | tr '[:upper:]' '[:lower:]')_$(uname -m | sed 's/x86_64/amd64/;s/aarch64/arm64/').tar.gz" | tar xz mcp-publisher
+          curl -L "https://github.com/modelcontextprotocol/registry/releases/download/v1.7.9/mcp-publisher_$(uname -s | tr '[:upper:]' '[:lower:]')_$(uname -m | sed 's/x86_64/amd64/;s/aarch64/arm64/').tar.gz" | tar xz mcp-publisher
 
       - name: Login to MCP Registry
         run: ./mcp-publisher login github-oidc