Adds an Output/Details tab bar to the agents page right-panel. The Details
tab renders AgentDetailsPanel, which surfaces agent metadata (status, mode,
provider, initiative link, task name, exit code), input files with a
file-picker UI, and the effective prompt text — all streamed via the new
getAgent/getAgentInputFiles/getAgentPrompt tRPC procedures.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>