feat(compat): package rename compatibility layer for oh-my-opencode → oh-my-openagent

- Add legacy plugin startup warning when oh-my-opencode config detected
- Update CLI installer and TUI installer for new package name
- Split monolithic config-manager.test.ts into focused test modules
- Add plugin config detection tests for legacy name fallback
- Update processed-command-store to use plugin-identity constants
- Add claude-code-plugin-loader discovery test for both config names
- Update chat-params and ultrawork-db tests for plugin identity

Part of #2823

src/shared/log-legacy-plugin-startup-warning.ts

@@ -0,0 +1,28 @@
+import { checkForLegacyPluginEntry } from "./legacy-plugin-warning"
+import { log } from "./logger"
+import { LEGACY_PLUGIN_NAME, PLUGIN_NAME } from "./plugin-identity"
+
+function toCanonicalEntry(entry: string): string {
+  if (entry === LEGACY_PLUGIN_NAME) {
+    return PLUGIN_NAME
+  }
+
+  if (entry.startsWith(`${LEGACY_PLUGIN_NAME}@`)) {
+    return `${PLUGIN_NAME}${entry.slice(LEGACY_PLUGIN_NAME.length)}`
+  }
+
+  return entry
+}
+
+export function logLegacyPluginStartupWarning(): void {
+  const result = checkForLegacyPluginEntry()
+  if (!result.hasLegacyEntry) {
+    return
+  }
+
+  log("[OhMyOpenCodePlugin] Legacy plugin entry detected in OpenCode config", {
+    legacyEntries: result.legacyEntries,
+    suggestedEntries: result.legacyEntries.map(toCanonicalEntry),
+    hasCanonicalEntry: result.hasCanonicalEntry,
+  })
+}