Studio: fix table overflow, agent filtering, and blank detail page

Studio UI bugs found after redesign:

1. Tables overflow on mobile

• "Running Agents" table overflows horizontally
• Task table also overflows
• Need responsive table design (horizontal scroll, or card layout on mobile)

2. "Running Agents" shows terminated agents

• Section labeled "Running Agents" but displays completed/failed agents too
• Should filter to only running, or rename section to "Recent Agents"
• Same issue as t-457 (agentd top) - need consistent filtering

3. Run ID links lead to blank page

• Clicking on a run ID in the agents table goes to blank page
• Likely missing route handler or template for agent detail view
• Should show: run details, status, cost, duration, log tail

Fix approach

• Tables: use overflow-x: auto wrapper, or switch to card layout on mobile
• Filtering: add status filter, default to running
• Detail page: implement agent detail view route + template