feat(start-work): add auto_commit config option

Add start_work.auto_commit configuration option to allow users to
disable the automatic commit step in the /start-work workflow.

When auto_commit is false:
- STEP 8: COMMIT ATOMIC UNIT is removed from orchestrator reminder
- STEP 9: PROCEED TO NEXT TASK becomes STEP 8

Resolves #2197

src/plugin/hooks/create-continuation-hooks.ts

@@ -111,6 +111,7 @@ export function createContinuationHooks(args: {
           isContinuationStopped: (sessionID: string) =>
             stopContinuationGuard?.isStopped(sessionID) ?? false,
           agentOverrides: pluginConfig.agents,
+          autoCommit: pluginConfig.start_work?.auto_commit,
         }))
     : null