Capture full container stdout/stderr logs

## Motivation

- Current implementation only captures container startup logs. Full runtime output is needed for `kubectl logs` support.

## Required Features

- Capture all container stdout/stderr throughout session lifecycle
- Persist logs beyond container termination
- Support log rotation/size limits for long-running sessions

## Impact

- **Agent**: Medium - Log capture and forwarding
- **Common**: Low - Log storage (Valkey/Redis or DB)

## Testing Scenarios

- Logs from entire session lifecycle are captured
- Logs persist after session termination
- Large log handling (rotation, truncation)
- Multi-container session log separation

JIRA Issue: BA-3869