refactor: consolidate MCP install config snippet generation

[simplesagar]

Summary

Consolidate the MCP install config/snippet generation logic into a single shared function to eliminate duplication and ensure consistency.

Current State

The snippet generation logic is duplicated in 2 places:

Location	What it generates
config_snippet.json.tmpl	JSON config for Claude Desktop/Cursor (via Go template)
impl.go:buildInstallConfigs()	Export endpoint configs (via Go structs)

Both produce identical output:

{
  "command": "npx",
  "args": ["mcp-remote@0.1.25", "<url>", "--header", "Header:${ENV_VAR}"],
  "env": { "ENV_VAR": "<your-value-here>" }
}

This means:

• mcp-remote@0.1.25 version is hardcoded in multiple places
• Command format can drift between surfaces
• Updates require changes in multiple files

Proposed Solution

Create a single shared buildStdioConfig() function and eliminate the template.

Files to Modify

File	Change
server/internal/mcpmetadata/impl.go	Add buildStdioConfig(), update buildInstallConfigs() and ServeInstallPage()
server/internal/mcpmetadata/config_snippet.json.tmpl	Delete

Implementation Steps

1. Create shared buildStdioConfig function - Returns *types.McpExportStdioConfig with command, args, and env
2. Update buildInstallConfigs - Use buildStdioConfig() for ClaudeDesktop and Cursor configs
3. Update ServeInstallPage - Replace template execution with JSON serialization of buildStdioConfig() result
4. Remove template - Delete config_snippet.json.tmpl and its embed directive

Benefits

• Single source of truth for versions and command formats
• Consistent output across install page, export endpoint, and UI
• Easier maintenance when mcp-remote version updates
• Less code overall (remove template + template parsing)

Related

• PR feat(mcp): add MCP JSON export API with API key authentication #1385 introduced the export endpoint with buildInstallConfigs()
• Install page uses config_snippet.json.tmpl template

Acceptance Criteria

• Create buildStdioConfig() function that builds stdio config for MCP clients
• Update buildInstallConfigs() to use buildStdioConfig()
• Update ServeInstallPage() to use buildStdioConfig() + JSON marshal instead of template
• Delete config_snippet.json.tmpl and remove embed directive
• Verify install page JSON snippet renders correctly
• Verify export endpoint configs match install page format
• Add/update tests for the shared builder
• Run linter: mise lint:server

[linear]

AGE-1252

[simplesagar]

This has been addressed as part of PR #1377. The DRY refactoring:

• Extracted buildStdioConfig() as the single source of truth for stdio config generation
• Deleted config_snippet.json.tmpl template
• Both export API and install page now use the same Go function
• Added comprehensive tests to verify format consistency

The PR will auto-close this issue when merged.