fix(opencode): address code review findings for cleanup and schema docs

- Add project boundary guard to removeEmptyParents() using path.resolve
  and startsWith check to prevent traversal outside projectDir (Augment)
- Fix JSDoc: "Recursively remove" -> "Walk up ancestor directories"
- Add user-visible migration log message when processing legacy_targets
- Document legacy_targets field in Installer Config Schema comment block
  in platform-codes.yaml (CodeRabbit + Augment)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tools/cli/installers/lib/ide/_config-driven.js

@@ -455,6 +455,7 @@ LOAD and execute from: {project-root}/{{bmadFolderName}}/{{path}}
   async cleanup(projectDir, options = {}) {
     // Migrate legacy target directories (e.g. .opencode/agent → .opencode/agents)
     if (this.installerConfig?.legacy_targets) {
+      if (!options.silent) await prompts.log.message('  Migrating legacy directories...');
       for (const legacyDir of this.installerConfig.legacy_targets) {
         await this.cleanupTarget(projectDir, legacyDir, options);
         await this.removeEmptyParents(projectDir, legacyDir);
@@ -540,17 +541,20 @@ LOAD and execute from: {project-root}/{{bmadFolderName}}/{{path}}
     }
   }
   /**
-   * Recursively remove empty directories walking up from dir toward projectDir
+   * Walk up ancestor directories from relativeDir toward projectDir, removing each if empty
    * Stops at projectDir boundary — never removes projectDir itself
    * @param {string} projectDir - Project root (boundary)
    * @param {string} relativeDir - Relative directory to start from
    */
   async removeEmptyParents(projectDir, relativeDir) {
+    const resolvedProject = path.resolve(projectDir);
     let current = relativeDir;
     let last = null;
     while (current && current !== '.' && current !== last) {
       last = current;
-      const fullPath = path.join(projectDir, current);
+      const fullPath = path.resolve(projectDir, current);
+      // Boundary guard: never traverse outside projectDir
+      if (!fullPath.startsWith(resolvedProject + path.sep) && fullPath !== resolvedProject) break;
       try {
         if (!(await fs.pathExists(fullPath))) {
           current = path.dirname(current);

tools/cli/installers/lib/ide/platform-codes.yaml

@@ -194,6 +194,8 @@ platforms:
 #   template_type: string                 # Default template type to use
 #   header_template: string (optional)    # Override for header/frontmatter template
 #   body_template: string (optional)      # Override for body/content template
+#   legacy_targets: array (optional)      # Old target dirs to clean up on reinstall (migration)
+#     - string                            # Relative path, e.g. .opencode/agent
 #   targets: array (optional)             # For multi-target installations
 #     - target_dir: string
 #       template_type: string