feat(gemini): add Gemini CLI as sixth target provider

Add `--to gemini` support for both `convert` and `install` commands,
converting Claude Code plugins into Gemini CLI-compatible format.

- Agents convert to `.gemini/skills/*/SKILL.md` with description frontmatter
- Commands convert to `.gemini/commands/*.toml` with TOML prompt format
- Namespaced commands create directory structure (workflows:plan -> workflows/plan.toml)
- Skills pass through unchanged (identical SKILL.md standard)
- MCP servers written to `.gemini/settings.json` with merge support
- Content transforms: .claude/ paths, Task calls, @agent references
- Hooks emit warning (different format in Gemini)

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

src/commands/convert.ts

@@ -23,7 +23,7 @@ export default defineCommand({
     to: {
       type: "string",
       default: "opencode",
-      description: "Target format (opencode | codex | droid | cursor | pi)",
+      description: "Target format (opencode | codex | droid | cursor | pi | gemini)",
     },
     output: {
       type: "string",
@@ -145,5 +145,6 @@ function resolveTargetOutputRoot(targetName: string, outputRoot: string, codexHo
   if (targetName === "pi") return piHome
   if (targetName === "droid") return path.join(os.homedir(), ".factory")
   if (targetName === "cursor") return path.join(outputRoot, ".cursor")
+  if (targetName === "gemini") return path.join(outputRoot, ".gemini")
   return outputRoot
 }

src/commands/install.ts

@@ -25,7 +25,7 @@ export default defineCommand({
     to: {
       type: "string",
       default: "opencode",
-      description: "Target format (opencode | codex | droid | cursor | pi)",
+      description: "Target format (opencode | codex | droid | cursor | pi | gemini)",
     },
     output: {
       type: "string",
@@ -183,6 +183,10 @@ function resolveTargetOutputRoot(
     const base = hasExplicitOutput ? outputRoot : process.cwd()
     return path.join(base, ".cursor")
   }
+  if (targetName === "gemini") {
+    const base = hasExplicitOutput ? outputRoot : process.cwd()
+    return path.join(base, ".gemini")
+  }
   return outputRoot
 }