fix(codex-link): isolate model transfers and widen local connection capacity

apps/desktop/electron/codex-link.test.ts

@@ -39,6 +39,7 @@ interface World {
   probesUntilUp: number
   autostart: null | string
   regFails: boolean
+  configWriteFails: boolean
   /** Every observable effect, in order. */
   events: string[]
   clock: number
@@ -59,6 +60,7 @@ function createWorld(patch: Partial<World> & { files?: Map<string, string> } = {
     staleVersion: null,
     probesUntilUp: 0,
     regFails: false,
+    configWriteFails: false,
     spawnWorks: true,
     ...patch
   }
@@ -71,6 +73,7 @@ function createWorld(patch: Partial<World> & { files?: Map<string, string> } = {
     exists: file => world.files.has(file),
     readText: file => world.files.get(file) ?? null,
     writeTextAtomic: (file, text) => {
+      if (file === PATHS.codexConfig && world.configWriteFails) throw new Error('config locked')
       world.events.push(`write ${file}`)
       world.files.set(file, text)
     },
@@ -332,6 +335,27 @@ describe('applyCodexLink', () => {
     expect(world.listening).toBe(false)
   })
 
+  it('keeps the bridge and login item if disconnect cannot restore the config', async () => {
+    const { link, world } = createWorld({ listening: true })
+    await link.apply()
+    const linkedConfig = world.files.get(PATHS.codexConfig)
+    const autostart = world.autostart
+    world.events.length = 0
+    world.configWriteFails = true
+
+    expect(await link.apply({ enabled: false })).toMatchObject({
+      bridgeRunning: true, lastError: 'config-write-failed'
+    })
+    expect(world.files.get(PATHS.codexConfig)).toBe(linkedConfig)
+    expect(world.autostart).toBe(autostart)
+    expect(world.events).not.toContain('stop')
+    expect(world.events).not.toContain('autostart clear')
+
+    world.configWriteFails = false
+    expect(await link.apply({ enabled: false })).toMatchObject({ bridgeRunning: false, lastError: null })
+    expect(world.files.get(PATHS.codexConfig)).toBe(USER_CONFIG)
+  })
+
   it('stays off across applies and comes back when turned on', async () => {
     const { link, world } = createWorld()
     world.files.set(PATHS.settingsFile, '{"enabled": false, "kapsam": "ide", "not": "ours"}')