Introduce the `execenv` package that creates isolated working directories
for each agent task. Supports git worktree mode (code tasks) and plain
directory mode (non-code tasks), with `.agent_context/issue_context.md`
injected into the workdir for Claude Code to discover.
Key changes:
- New `server/internal/daemon/execenv/` package (Prepare/Cleanup)
- `runTask()` now creates isolated env instead of using shared reposRoot
- Prompt updated to reference `.agent_context/` files
- Add `WorkspacesRoot` config (default ~/multica_workspaces)
- Add `KeepEnvAfterTask` config for debugging
- Default agent timeout increased from 20min to 2h
- `CompleteTask` now forwards branch name to server
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
