feat(B.1): add tasks.assignee column + claim semantics on task start

Schema:
- Added `assignee TEXT` column to tasks table (Drizzle schema + migration)
- Added `idx_tasks_assignee` index for query performance
- Migration: 20260325010000_add-assignee-column

Contracts:
- Task interface: added `assignee?: string | null`
- TaskFieldUpdates: added `assignee?: string | null`
- DataAccessor.updateTaskFields() accepts assignee

Core:
- converters.ts: rowToTask/taskToRow handle assignee
- db-helpers.ts: upsert includes assignee
- task-store.ts: updateTask handles assignee field
- sqlite-data-accessor.ts: updateTaskFields field map includes assignee
- task-work/index.ts: startTask() auto-sets assignee from CLEO_AGENT_ID
  (claim semantics — /claim verb maps to tasks.start via nexus.route)

Also: fixed stale @ts-expect-error in lafs tokenEstimator.ts
(Intl.Segmenter now in TS 5.9 lib types)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kryptobaseddev

drizzle/migrations/drizzle-tasks/20260325010000_add-assignee-column/migration.sql

@@ -0,0 +1,2 @@
+ALTER TABLE tasks ADD COLUMN assignee TEXT;--> statement-breakpoint
+CREATE INDEX idx_tasks_assignee ON tasks (assignee);

packages/contracts/src/data-accessor.ts

@@ -103,6 +103,7 @@ export interface TaskFieldUpdates {
   modifiedBy?: string | null;
   sessionId?: string | null;
   updatedAt?: string | null;
+  assignee?: string | null;
 }
 
 /**

packages/contracts/src/task.ts

@@ -214,6 +214,9 @@ export interface Task {
    * @task T060
    */
   pipelineStage?: string | null;
+
+  /** Agent ID that has claimed/is assigned to this task. Null when unclaimed. */
+  assignee?: string | null;
 }
 
 // ---------------------------------------------------------------------------

packages/core/src/store/converters.ts

@@ -57,6 +57,7 @@ export function rowToTask(row: TaskRow): Task {
           }
         : undefined,
     pipelineStage: row.pipelineStage ?? undefined,
+    assignee: row.assignee ?? undefined,
   };
 }
 
@@ -92,6 +93,7 @@ export function taskToRow(task: Partial<Task> & { id: string }): NewTaskRow {
     modifiedBy: task.provenance?.modifiedBy ?? null,
     sessionId: task.provenance?.sessionId ?? null,
     pipelineStage: task.pipelineStage ?? null,
+    assignee: task.assignee ?? null,
   };
 }
 

packages/core/src/store/db-helpers.ts

@@ -79,6 +79,7 @@ export async function upsertTask(
     sessionId: row.sessionId,
     // T060: pipeline stage name (RCASD-IVTR+C)
     pipelineStage: row.pipelineStage ?? null,
+    assignee: row.assignee ?? null,
     // Always include archive metadata so unarchive clears stale values (T5034)
     archivedAt: archiveFields?.archivedAt ?? null,
     archiveReason: archiveFields?.archiveReason ?? null,

packages/core/src/store/sqlite-data-accessor.ts

@@ -783,6 +783,7 @@ export async function createSqliteDataAccessor(cwd?: string): Promise<DataAccess
         ['createdBy', 'createdBy'],
         ['modifiedBy', 'modifiedBy'],
         ['sessionId', 'sessionId'],
+        ['assignee', 'assignee'],
       ];
 
       for (const [key, col] of fieldMap) {

packages/core/src/store/task-store.ts

@@ -99,6 +99,7 @@ export async function updateTask(
     updateRow.cancellationReason = updates.cancellationReason;
   if (updates.verification !== undefined)
     updateRow.verificationJson = JSON.stringify(updates.verification);
+  if (updates.assignee !== undefined) updateRow.assignee = updates.assignee;
 
   db.update(schema.tasks).set(updateRow).where(eq(schema.tasks.id, taskId)).run();
 

packages/core/src/store/tasks-schema.ts

@@ -196,6 +196,8 @@ export const tasks = sqliteTable(
     // Not referencing lifecycle_stages.id so that stage binding works without
     // requiring a lifecycle pipeline record for every task.
     pipelineStage: text('pipeline_stage'),
+    /** Agent ID that has claimed/is assigned to this task. */
+    assignee: text('assignee'),
   },
   (table) => [
     index('idx_tasks_status').on(table.status),
@@ -205,6 +207,7 @@ export const tasks = sqliteTable(
     index('idx_tasks_priority').on(table.priority),
     index('idx_tasks_session_id').on(table.sessionId),
     index('idx_tasks_pipeline_stage').on(table.pipelineStage),
+    index('idx_tasks_assignee').on(table.assignee),
     // T033 composite indexes
     index('idx_tasks_parent_status').on(table.parentId, table.status),
     index('idx_tasks_status_priority').on(table.status, table.priority),

packages/core/src/task-work/index.ts

@@ -113,6 +113,11 @@ export async function startTask(
 
   await acc.setMetaValue('focus_state', focus);
 
+  // Set assignee on the task (claim semantics)
+  if (!task.assignee) {
+    await acc.updateTaskFields(taskId, { assignee: process.env['CLEO_AGENT_ID'] ?? 'local' });
+  }
+
   await logOperation(
     'task_start',
     taskId,