refactor(task): align continuation ids with task_id

src/tools/delegate-task/tools.ts

@@ -84,13 +84,14 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
   ${categoryList}
   - subagent_type: Use specific agent directly (explore, librarian, oracle, metis, momus)
   - run_in_background: REQUIRED. true=async (returns task_id), false=sync (waits). Use background=true ONLY for parallel exploration with 5+ independent queries.
-  - session_id: Existing Task session to continue (from previous task output). Continues agent with FULL CONTEXT PRESERVED - saves tokens, maintains continuity.
+  - task_id: Existing task to continue (from previous task output). Continues the same subagent session with FULL CONTEXT PRESERVED.
+  - session_id: Deprecated alias for task_id. Accepted for backward compatibility.
   - command: The command that triggered this task (optional, for slash command tracking).
   
-  **WHEN TO USE session_id:**
-  - Task failed/incomplete → session_id with "fix: [specific issue]"
-  - Need follow-up on previous result → session_id with additional question
-  - Multi-turn conversation with same agent → always session_id instead of new task
+  **WHEN TO USE task_id:**
+  - Task failed/incomplete → task_id with "fix: [specific issue]"
+  - Need follow-up on previous result → task_id with additional question
+  - Multi-turn conversation with same agent → always task_id instead of new task
   
   Prompts MUST be in English.`
 
@@ -103,11 +104,15 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
       run_in_background: tool.schema.boolean().describe("REQUIRED. true=async (returns task_id), false=sync (waits). Use false for task delegation, true ONLY for parallel exploration."),
       category: tool.schema.string().optional().describe(`REQUIRED if subagent_type not provided. Do NOT provide both category and subagent_type.`),
       subagent_type: tool.schema.string().optional().describe("REQUIRED if category not provided. Do NOT provide both category and subagent_type."),
-      session_id: tool.schema.string().optional().describe("Existing Task session to continue"),
+      task_id: tool.schema.string().optional().describe("Existing task to continue. Canonical resume identifier."),
+      session_id: tool.schema.string().optional().describe("Deprecated alias for task_id. Existing task to continue."),
       command: tool.schema.string().optional().describe("The command that triggered this task"),
     },
     async execute(args: DelegateTaskArgs, toolContext) {
       const ctx = toolContext as ToolContextWithMetadata
+      if (!args.task_id && args.session_id) {
+        args.task_id = args.session_id
+      }
 
       if (args.category) {
         if (args.subagent_type && args.subagent_type !== SISYPHUS_JUNIOR_AGENT) {
@@ -158,7 +163,7 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
 
       const parentContext = await resolveParentContext(ctx, options.client)
 
-      if (args.session_id) {
+      if (args.task_id || args.session_id) {
         if (runInBackground) {
           return executeBackgroundContinuation(args, ctx, options, parentContext)
         }