refactor: remove built-in Google auth in favor of external plugin

- Delete src/auth/antigravity/ directory (28 files)
- Delete src/google-auth.ts standalone wrapper
- Delete src/cli/commands/auth.ts CLI command
- Remove google_auth config option from schema
- Update CLI to remove auth command registration
- Update config-manager to remove google_auth handling
- Update documentation to reference external opencode-antigravity-auth plugin only
- Regenerate JSON schema

Users should install the opencode-antigravity-auth plugin for Gemini authentication.

BREAKING CHANGE: The google_auth config option is removed. Use the external plugin instead.

src/cli/config-manager.ts

@@ -267,10 +267,6 @@ export function generateOmoConfig(installConfig: InstallConfig): Record<string,
     $schema: "https://raw.githubusercontent.com/code-yeongyu/oh-my-opencode/master/assets/oh-my-opencode.schema.json",
   }
 
-  if (installConfig.hasGemini) {
-    config.google_auth = false
-  }
-
   const agents: Record<string, Record<string, unknown>> = {}
 
   if (!installConfig.hasClaude) {
@@ -642,7 +638,6 @@ export function addProviderConfig(config: InstallConfig): ConfigMergeResult {
 }
 
 interface OmoConfigData {
-  google_auth?: boolean
   agents?: Record<string, { model?: string }>
 }
 
@@ -713,9 +708,6 @@ export function detectCurrentConfig(): DetectedConfig {
       result.hasChatGPT = false
     }
 
-    if (omoConfig.google_auth === false) {
-      result.hasGemini = plugins.some((p) => p.startsWith("opencode-antigravity-auth"))
-    }
   } catch {
     /* intentionally empty - malformed omo config returns defaults from opencode config detection */
   }

src/cli/index.ts

@@ -4,7 +4,6 @@ import { install } from "./install"
 import { run } from "./run"
 import { getLocalVersion } from "./get-local-version"
 import { doctor } from "./doctor"
-import { listAccounts, removeAccount } from "./commands/auth"
 import type { InstallArgs } from "./types"
 import type { RunOptions } from "./run"
 import type { GetLocalVersionOptions } from "./get-local-version/types"
@@ -135,45 +134,6 @@ Categories:
     process.exit(exitCode)
   })
 
-const authCommand = program
-  .command("auth")
-  .description("Manage Google Antigravity accounts")
-
-authCommand
-  .command("list")
-  .description("List all Google Antigravity accounts")
-  .addHelpText("after", `
-Examples:
-  $ bunx oh-my-opencode auth list
-
-Shows:
-  - Account index and email
-  - Account tier (free/paid)
-  - Active account (marked with *)
-  - Rate limit status per model family
-`)
-  .action(async () => {
-    const exitCode = await listAccounts()
-    process.exit(exitCode)
-  })
-
-authCommand
-  .command("remove <index-or-email>")
-  .description("Remove an account by index or email")
-  .addHelpText("after", `
-Examples:
-  $ bunx oh-my-opencode auth remove 0
-  $ bunx oh-my-opencode auth remove user@example.com
-
-Note:
-  - Use 'auth list' to see account indices
-  - Removing the active account will switch to the next available account
-`)
-  .action(async (indexOrEmail: string) => {
-    const exitCode = await removeAccount(indexOrEmail)
-    process.exit(exitCode)
-  })
-
 program
   .command("version")
   .description("Show version information")