ci: pin MCP Publisher to v1.2.3

Update GitHub Actions workflow to use specific version of MCP Publisher instead of latest to ensure build reproducibility.

Author: ahonn

.github/workflows/publish-mcp.yml

@@ -41,7 +41,7 @@ jobs:
 
       - name: Install MCP Publisher
         run: |
-          curl -L "https://github.com/modelcontextprotocol/registry/releases/download/latest/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/v1.2.3/mcp-publisher_1.2.3_$(uname -s | tr '[:upper:]' '[:lower:]')_$(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