fix(publisher): honor mcpName as the authoritative server name in init (#1195)

## Summary

Follow-up to #1145. When `mcpName` is set in `package.json`, it should
be the server name used by `mcp-publisher init`. Two issues addressed:

### 1. `getNameFromPackageJSON` mangled `mcpName` through npm-name
transformation

`mcpName` values are already in MCP server name format (e.g.
`io.github.foo/bar`). The existing code ran them through the
`@scope/name → io.github.scope/name` transform and its
`io.github.<your-username>/*` fallback, producing a broken double-prefix
result.

Example with `"mcpName": "io.github.acme/weather"`:
- Before: `io.github.<your-username>/io.github.acme/weather` ❌
- After: `io.github.acme/weather` ✅

### 2. `detectServerName` consulted git before `mcpName`

Even with `mcpName` set in `package.json`, a github.com git remote (or a
`repository` field) silently won — the function returned
`io.github.<owner>/<repo>` and never looked at `mcpName`. Per the
[quickstart
docs](https://github.com/modelcontextprotocol/registry/blob/main/docs/modelcontextprotocol-io/quickstart.mdx),
*"The value of `mcpName` will be your server's name in the MCP
Registry"*, so `mcpName` should take precedence.

## Changes

- `cmd/publisher/commands/init.go`:
- New `getMcpNameFromPackageJSON()` helper that returns `mcpName` or
`""`.
- `detectServerName` checks `mcpName` first, before git remote and the
`name`-based fallback.
- `getNameFromPackageJSON` simplified — the now-redundant `mcpName`
branch was removed; it only handles the npm `name` transformation.
- `cmd/publisher/commands/init_test.go` (new): 5 cases through the
public `InitCommand` API covering `mcpName` as-is, fallback to scoped
`name`, fallback to placeholder, version fallback, and `mcpName` winning
over a GitHub `repository` URL.

This completes the fix for #737.

## Test plan

- [x] `go test ./cmd/publisher/commands/` passes (5 new subtests)
- [x] `golangci-lint run ./cmd/publisher/commands/` clean
- [ ] Manual: `mcp-publisher init` in a git-tracked directory with
`package.json` containing `mcpName` produces a `server.json` whose
`name` matches `mcpName`, not the repo slug

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/publisher/commands/init.go

@@ -132,6 +132,26 @@ func detectSubfolder() string {
 	return filepath.ToSlash(relPath)
 }
 
+// getMcpNameFromPackageJSON returns the `mcpName` field from package.json, or
+// "" if not set. mcpName is the authoritative MCP server name when present —
+// see docs/modelcontextprotocol-io/quickstart.mdx.
+func getMcpNameFromPackageJSON() string {
+	data, err := os.ReadFile("package.json")
+	if err != nil {
+		return ""
+	}
+
+	var pkg map[string]any
+	if err := json.Unmarshal(data, &pkg); err != nil {
+		return ""
+	}
+
+	if mcpName, ok := pkg["mcpName"].(string); ok && mcpName != "" {
+		return mcpName
+	}
+	return ""
+}
+
 func getNameFromPackageJSON() string {
 	data, err := os.ReadFile("package.json")
 	if err != nil {
@@ -143,17 +163,13 @@ func getNameFromPackageJSON() string {
 		return ""
 	}
 
-	// Prefer mcpName over name, as the server name must match mcpName
-	name, ok := pkg["mcpName"].(string)
+	name, ok := pkg["name"].(string)
 	if !ok || name == "" {
-		name, ok = pkg["name"].(string)
-		if !ok || name == "" {
-			return ""
-		}
+		return ""
 	}
 
 	// Convert npm package name to MCP server name
-	// @org/package -> io.npm.org/package
+	// @org/package -> io.github.org/package
 	if strings.HasPrefix(name, "@") {
 		parts := strings.Split(name[1:], "/")
 		if len(parts) == 2 {
@@ -183,6 +199,13 @@ func getVersionFromPackageJSON() string {
 }
 
 func detectServerName(subfolder string) string {
+	// mcpName in package.json is the authoritative server name when set, so it
+	// takes precedence over names inferred from the git remote or the npm
+	// `name` field.
+	if name := getMcpNameFromPackageJSON(); name != "" {
+		return name
+	}
+
 	// Try to get from git remote
 	repoURL := detectRepoURL()
 	if repoURL != "" && strings.Contains(repoURL, "github.com") {