Remove demo/sample Kanban tasks

These were placeholder seed data shipped with the repo (a demo
'Fix login bug' task and a 'Test kanban task' with a canned
'Waiting for API review' block reason) - not real tasks. Clearing
them so the board starts empty.

data/kanban/0f822987.json

@@ -1,12 +0,0 @@
-{
-  "id": "0f822987",
-  "title": "Fix login bug",
-  "body": "The login page has a race condition",
-  "status": "todo",
-  "priority": "high",
-  "assignee": "opencode",
-  "comments": [],
-  "links": [],
-  "created": "2026-06-05T09:52:18.236452+00:00",
-  "updated": "2026-06-05T09:52:18.236473+00:00"
-}

data/kanban/8893ad14.json

@@ -1,15 +0,0 @@
-{
-  "id": "8893ad14",
-  "title": "Test kanban task",
-  "body": "",
-  "status": "blocked",
-  "priority": "medium",
-  "assignee": "",
-  "comments": [],
-  "links": [],
-  "created": "2026-06-05T09:50:30.293643+00:00",
-  "updated": "2026-06-05T09:52:18.274595+00:00",
-  "summary": "Test done",
-  "completed_at": "2026-06-05T09:50:46.473612+00:00",
-  "block_reason": "Waiting for API review"
-}