fix(#2823): auto-migrate legacy plugin name and warn users at startup

- logLegacyPluginStartupWarning now emits console.warn (visible to user,
  not just log file) when oh-my-opencode is detected in opencode.json
- Auto-migrates opencode.json plugin entry from oh-my-opencode to
  oh-my-openagent (with backup)
- plugin-config.ts: add console.warn when loading legacy config filename
- test: 10 tests covering migration, console output, edge cases

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

@@ -1,4 +1,4 @@
-import { afterAll, beforeEach, describe, expect, it, mock } from "bun:test"
+import { afterAll, afterEach, beforeEach, describe, expect, it, mock, spyOn } from "bun:test"
 import type { LegacyPluginCheckResult } from "./legacy-plugin-warning"
 
 function createLegacyPluginCheckResult(
@@ -8,13 +8,15 @@ function createLegacyPluginCheckResult(
     hasLegacyEntry: false,
     hasCanonicalEntry: false,
     legacyEntries: [],
+    configPath: null,
     ...overrides,
   }
 }
 
 const mockCheckForLegacyPluginEntry = mock(() => createLegacyPluginCheckResult())
-
 const mockLog = mock(() => {})
+const mockMigrateLegacyPluginEntry = mock(() => false)
+let consoleWarnSpy: ReturnType<typeof spyOn>
 
 mock.module("./legacy-plugin-warning", () => ({
   checkForLegacyPluginEntry: mockCheckForLegacyPluginEntry,
@@ -24,6 +26,10 @@ mock.module("./logger", () => ({
   log: mockLog,
 }))
 
+mock.module("./migrate-legacy-plugin-entry", () => ({
+  migrateLegacyPluginEntry: mockMigrateLegacyPluginEntry,
+}))
+
 afterAll(() => {
   mock.restore()
 })
@@ -36,16 +42,24 @@ describe("logLegacyPluginStartupWarning", () => {
   beforeEach(() => {
     mockCheckForLegacyPluginEntry.mockReset()
     mockLog.mockReset()
+    mockMigrateLegacyPluginEntry.mockReset()
+    consoleWarnSpy = spyOn(console, "warn").mockImplementation(() => {})
 
     mockCheckForLegacyPluginEntry.mockReturnValue(createLegacyPluginCheckResult())
+    mockMigrateLegacyPluginEntry.mockReturnValue(false)
+  })
+
+  afterEach(() => {
+    consoleWarnSpy?.mockRestore()
   })
 
   describe("#given OpenCode config contains legacy plugin entries", () => {
-    it("logs the legacy entries with canonical replacements", async () => {
+    it("#then logs the legacy entries with canonical replacements", async () => {
       //#given
       mockCheckForLegacyPluginEntry.mockReturnValue(createLegacyPluginCheckResult({
         hasLegacyEntry: true,
         legacyEntries: ["oh-my-opencode", "oh-my-opencode@3.13.1"],
+        configPath: "/tmp/opencode.json",
       }))
       const { logLegacyPluginStartupWarning } = await importFreshStartupWarningModule()
 
@@ -63,10 +77,45 @@ describe("logLegacyPluginStartupWarning", () => {
         },
       )
     })
+
+    it("#then emits console.warn about the rename", async () => {
+      //#given
+      mockCheckForLegacyPluginEntry.mockReturnValue(createLegacyPluginCheckResult({
+        hasLegacyEntry: true,
+        legacyEntries: ["oh-my-opencode@latest"],
+        configPath: "/tmp/opencode.json",
+      }))
+      const { logLegacyPluginStartupWarning } = await importFreshStartupWarningModule()
+
+      //#when
+      logLegacyPluginStartupWarning()
+
+      //#then
+      expect(consoleWarnSpy).toHaveBeenCalled()
+      const firstCall = consoleWarnSpy.mock.calls[0]?.[0] as string
+      expect(firstCall).toContain("oh-my-opencode")
+      expect(firstCall).toContain("oh-my-openagent")
+    })
+
+    it("#then attempts auto-migration of the opencode.json", async () => {
+      //#given
+      mockCheckForLegacyPluginEntry.mockReturnValue(createLegacyPluginCheckResult({
+        hasLegacyEntry: true,
+        legacyEntries: ["oh-my-opencode"],
+        configPath: "/tmp/opencode.json",
+      }))
+      const { logLegacyPluginStartupWarning } = await importFreshStartupWarningModule()
+
+      //#when
+      logLegacyPluginStartupWarning()
+
+      //#then
+      expect(mockMigrateLegacyPluginEntry).toHaveBeenCalledWith("/tmp/opencode.json")
+    })
   })
 
   describe("#given OpenCode config uses only canonical plugin entries", () => {
-    it("does not log a startup warning", async () => {
+    it("#then does not log a startup warning", async () => {
       //#given
       const { logLegacyPluginStartupWarning } = await importFreshStartupWarningModule()
 
@@ -75,6 +124,27 @@ describe("logLegacyPluginStartupWarning", () => {
 
       //#then
       expect(mockLog).not.toHaveBeenCalled()
+      expect(consoleWarnSpy).not.toHaveBeenCalled()
+    })
+  })
+
+  describe("#given migration succeeds", () => {
+    it("#then logs success message to console", async () => {
+      //#given
+      mockCheckForLegacyPluginEntry.mockReturnValue(createLegacyPluginCheckResult({
+        hasLegacyEntry: true,
+        legacyEntries: ["oh-my-opencode@latest"],
+        configPath: "/tmp/opencode.json",
+      }))
+      mockMigrateLegacyPluginEntry.mockReturnValue(true)
+      const { logLegacyPluginStartupWarning } = await importFreshStartupWarningModule()
+
+      //#when
+      logLegacyPluginStartupWarning()
+
+      //#then
+      const calls = consoleWarnSpy.mock.calls.map((c) => c[0] as string)
+      expect(calls.some((c) => c.includes("Auto-migrated"))).toBe(true)
     })
   })
 })