refactor(tmux-subagent): state-first architecture with decision engine (#1125)

* refactor(tmux-subagent): add state-first architecture with decision engine

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

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

* feat(tmux): add pane spawn callbacks for background and sync sessions

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

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

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/features/tmux-subagent/action-executor.ts

@@ -0,0 +1,66 @@
+import type { TmuxConfig } from "../../config/schema"
+import type { PaneAction } from "./types"
+import { spawnTmuxPane, closeTmuxPane } from "../../shared/tmux"
+import { log } from "../../shared"
+
+export interface ActionResult {
+  success: boolean
+  paneId?: string
+  error?: string
+}
+
+export interface ExecuteActionsResult {
+  success: boolean
+  spawnedPaneId?: string
+  results: Array<{ action: PaneAction; result: ActionResult }>
+}
+
+export async function executeAction(
+  action: PaneAction,
+  config: TmuxConfig,
+  serverUrl: string
+): Promise<ActionResult> {
+  if (action.type === "close") {
+    const success = await closeTmuxPane(action.paneId)
+    return { success }
+  }
+
+  const result = await spawnTmuxPane(
+    action.sessionId,
+    action.description,
+    config,
+    serverUrl,
+    action.targetPaneId
+  )
+
+  return {
+    success: result.success,
+    paneId: result.paneId,
+  }
+}
+
+export async function executeActions(
+  actions: PaneAction[],
+  config: TmuxConfig,
+  serverUrl: string
+): Promise<ExecuteActionsResult> {
+  const results: Array<{ action: PaneAction; result: ActionResult }> = []
+  let spawnedPaneId: string | undefined
+
+  for (const action of actions) {
+    log("[action-executor] executing", { type: action.type })
+    const result = await executeAction(action, config, serverUrl)
+    results.push({ action, result })
+
+    if (!result.success) {
+      log("[action-executor] action failed", { type: action.type, error: result.error })
+      return { success: false, results }
+    }
+
+    if (action.type === "spawn" && result.paneId) {
+      spawnedPaneId = result.paneId
+    }
+  }
+
+  return { success: true, spawnedPaneId, results }
+}