fix: address code review findings for gemini target

- Extract named GeminiMcpServer type (eliminates NonNullable indexing)
- Deep-merge mcpServers in settings.json (preserves existing entries)
- Warn when existing settings.json cannot be parsed
- Add test for uniqueName dedup (agent/skill name collision)
- Add test for TOML triple-quote escaping

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

src/converters/claude-to-gemini.ts

@@ -1,6 +1,6 @@
 import { formatFrontmatter } from "../utils/frontmatter"
 import type { ClaudeAgent, ClaudeCommand, ClaudeMcpServer, ClaudePlugin } from "../types/claude"
-import type { GeminiBundle, GeminiCommand, GeminiSkill } from "../types/gemini"
+import type { GeminiBundle, GeminiCommand, GeminiMcpServer, GeminiSkill } from "../types/gemini"
 import type { ClaudeToOpenCodeOptions } from "./claude-to-opencode"
 
 export type ClaudeToGeminiOptions = ClaudeToOpenCodeOptions
@@ -109,12 +109,12 @@ export function transformContentForGemini(body: string): string {
 
 function convertMcpServers(
   servers?: Record<string, ClaudeMcpServer>,
-): GeminiBundle["mcpServers"] | undefined {
+): Record<string, GeminiMcpServer> | undefined {
   if (!servers || Object.keys(servers).length === 0) return undefined
 
-  const result: NonNullable<GeminiBundle["mcpServers"]> = {}
+  const result: Record<string, GeminiMcpServer> = {}
   for (const [name, server] of Object.entries(servers)) {
-    const entry: NonNullable<GeminiBundle["mcpServers"]>[string] = {}
+    const entry: GeminiMcpServer = {}
     if (server.command) {
       entry.command = server.command
       if (server.args && server.args.length > 0) entry.args = server.args

src/targets/gemini.ts

@@ -37,11 +37,14 @@ export async function writeGeminiBundle(outputRoot: string, bundle: GeminiBundle
       try {
         existingSettings = await readJson<Record<string, unknown>>(settingsPath)
       } catch {
-        // If existing file is invalid JSON, start fresh
+        console.warn("Warning: existing settings.json could not be parsed and will be replaced.")
       }
     }
 
-    const merged = { ...existingSettings, mcpServers: bundle.mcpServers }
+    const existingMcp = (existingSettings.mcpServers && typeof existingSettings.mcpServers === "object")
+      ? existingSettings.mcpServers as Record<string, unknown>
+      : {}
+    const merged = { ...existingSettings, mcpServers: { ...existingMcp, ...bundle.mcpServers } }
     await writeJson(settingsPath, merged)
   }
 }

src/types/gemini.ts

@@ -13,15 +13,17 @@ export type GeminiCommand = {
   content: string // Full TOML content
 }
 
+export type GeminiMcpServer = {
+  command?: string
+  args?: string[]
+  env?: Record<string, string>
+  url?: string
+  headers?: Record<string, string>
+}
+
 export type GeminiBundle = {
   generatedSkills: GeminiSkill[] // From agents
   skillDirs: GeminiSkillDir[] // From skills (pass-through)
   commands: GeminiCommand[]
-  mcpServers?: Record<string, {
-    command?: string
-    args?: string[]
-    env?: Record<string, string>
-    url?: string
-    headers?: Record<string, string>
-  }>
+  mcpServers?: Record<string, GeminiMcpServer>
 }