fix(start-work): restore atlas native command routing

Route the builtin /start-work command to Atlas when Atlas is available so OpenCode resolves the native command agent correctly before plugin hooks run.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/features/builtin-commands/commands.test.ts

@@ -1,8 +1,17 @@
-import { describe, test, expect } from "bun:test"
+import { afterEach, beforeEach, describe, test, expect } from "bun:test"
 import { loadBuiltinCommands } from "./commands"
 import { HANDOFF_TEMPLATE } from "./templates/handoff"
 import { REMOVE_AI_SLOPS_TEMPLATE } from "./templates/remove-ai-slops"
 import type { BuiltinCommandName } from "./types"
+import { _resetForTesting, registerAgentName } from "../claude-code-session-state"
+
+beforeEach(() => {
+  _resetForTesting()
+})
+
+afterEach(() => {
+  _resetForTesting()
+})
 
 describe("loadBuiltinCommands", () => {
   test("should include handoff command in loaded commands", () => {
@@ -69,6 +78,17 @@ describe("loadBuiltinCommands", () => {
     //#then
     expect(commands["start-work"].agent).toBe("sisyphus")
   })
+
+  test("should preassign Atlas as the native agent for start-work when Atlas is registered", () => {
+    //#given
+    registerAgentName("atlas")
+
+    //#when
+    const commands = loadBuiltinCommands()
+
+    //#then
+    expect(commands["start-work"].agent).toBe("atlas")
+  })
 })
 
 describe("loadBuiltinCommands — remove-ai-slops", () => {

src/features/builtin-commands/commands.ts

@@ -1,4 +1,5 @@
 import type { CommandDefinition } from "../claude-code-command-loader"
+import { isAgentRegistered } from "../claude-code-session-state"
 import type { BuiltinCommandName, BuiltinCommands } from "./types"
 import { INIT_DEEP_TEMPLATE } from "./templates/init-deep"
 import { RALPH_LOOP_TEMPLATE, ULW_LOOP_TEMPLATE, CANCEL_RALPH_TEMPLATE } from "./templates/ralph-loop"
@@ -8,7 +9,8 @@ import { START_WORK_TEMPLATE } from "./templates/start-work"
 import { HANDOFF_TEMPLATE } from "./templates/handoff"
 import { REMOVE_AI_SLOPS_TEMPLATE } from "./templates/remove-ai-slops"
 
-const BUILTIN_COMMAND_DEFINITIONS: Record<BuiltinCommandName, Omit<CommandDefinition, "name">> = {
+function createBuiltinCommandDefinitions(): Record<BuiltinCommandName, Omit<CommandDefinition, "name">> {
+  return {
     "init-deep": {
       description: "(builtin) Initialize hierarchical AGENTS.md knowledge base",
       template: `<command-instruction>
@@ -58,7 +60,7 @@ ${REFACTOR_TEMPLATE}
     },
     "start-work": {
       description: "(builtin) Start Sisyphus work session from Prometheus plan",
-    agent: "sisyphus",
+      agent: isAgentRegistered("atlas") ? "atlas" : "sisyphus",
       template: `<command-instruction>
 ${START_WORK_TEMPLATE}
 </command-instruction>
@@ -106,14 +108,16 @@ $ARGUMENTS
       argumentHint: "[goal]",
     },
   }
+}
 
 export function loadBuiltinCommands(
   disabledCommands?: BuiltinCommandName[]
 ): BuiltinCommands {
+  const builtinCommandDefinitions = createBuiltinCommandDefinitions()
   const disabled = new Set(disabledCommands ?? [])
   const commands: BuiltinCommands = {}
 
-  for (const [name, definition] of Object.entries(BUILTIN_COMMAND_DEFINITIONS)) {
+  for (const [name, definition] of Object.entries(builtinCommandDefinitions)) {
     if (!disabled.has(name as BuiltinCommandName)) {
       const { argumentHint: _argumentHint, ...openCodeCompatible } = definition
       commands[name] = { ...openCodeCompatible, name } as CommandDefinition