docs: update all GitHub URLs from oh-my-opencode to oh-my-openagent

The GitHub repository was renamed from oh-my-opencode to oh-my-openagent,
but all documentation, scripts, and source code references still pointed
to the old repository name. This caused confusion for users who saw
'oh-my-opencode' in docs but a different repo name on GitHub.

Updated all references across:
- README files (en, ko, ja, zh-cn, ru)
- CONTRIBUTING.md
- docs/ (installation, overview, configuration, etc.)
- Source code (schema URLs, GitHub API calls, issue links)
- Test snapshots

The npm package name remains 'oh-my-opencode' (unchanged).

Fixes: https://x.com/Dhruv14588676/status/2031216617762468348

src/agents/builtin-agents.ts

@@ -82,7 +82,7 @@ export async function createBuiltinAgents(
   )
   // IMPORTANT: Do NOT call OpenCode client APIs during plugin initialization.
   // This function is called from config handler, and calling client API causes deadlock.
-  // See: https://github.com/code-yeongyu/oh-my-opencode/issues/1301
+  // See: https://github.com/code-yeongyu/oh-my-openagent/issues/1301
   const availableModels = await fetchAvailableModels(undefined, {
     connectedProviders: mergedConnectedProviders.length > 0 ? mergedConnectedProviders : undefined,
   })

src/agents/env-context.ts

@@ -2,7 +2,7 @@
  * Creates OmO-specific environment context (timezone, locale).
  * Note: Working directory, platform, and date are already provided by OpenCode's system.ts,
  * so we only include fields that OpenCode doesn't provide to avoid duplication.
- * See: https://github.com/code-yeongyu/oh-my-opencode/issues/379
+ * See: https://github.com/code-yeongyu/oh-my-openagent/issues/379
  */
 export function createEnvContext(): string {
   const timezone = Intl.DateTimeFormat().resolvedOptions().timeZone