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/cli/cli-installer.ts

@@ -1,4 +1,5 @@
 import color from "picocolors"
+import { PLUGIN_NAME } from "../shared"
 import type { InstallArgs } from "./types"
 import {
   addPluginToOpenCodeConfig,
@@ -32,7 +33,7 @@ export async function runCliInstaller(args: InstallArgs, version: string): Promi
     }
     console.log()
     printInfo(
-      "Usage: bunx oh-my-opencode install --no-tui --claude=<no|yes|max20> --gemini=<no|yes> --copilot=<no|yes>",
+      `Usage: bunx ${PLUGIN_NAME} install --no-tui --claude=<no|yes|max20> --gemini=<no|yes> --copilot=<no|yes>`,
     )
     console.log()
     return 1
@@ -65,7 +66,7 @@ export async function runCliInstaller(args: InstallArgs, version: string): Promi
 
   const config = argsToConfig(args)
 
-  printStep(step++, totalSteps, "Adding oh-my-opencode plugin...")
+  printStep(step++, totalSteps, `Adding ${PLUGIN_NAME} plugin...`)
   const pluginResult = await addPluginToOpenCodeConfig(version)
   if (!pluginResult.success) {
     printError(`Failed: ${pluginResult.error}`)
@@ -75,7 +76,7 @@ export async function runCliInstaller(args: InstallArgs, version: string): Promi
     `Plugin ${isUpdate ? "verified" : "added"} ${SYMBOLS.arrow} ${color.dim(pluginResult.configPath)}`,
   )
 
-  printStep(step++, totalSteps, "Writing oh-my-opencode configuration...")
+  printStep(step++, totalSteps, `Writing ${PLUGIN_NAME} configuration...`)
   const omoResult = writeOmoConfig(config)
   if (!omoResult.success) {
     printError(`Failed: ${omoResult.error}`)