Add workflow log listing & tail support (backend API + Tasks UI)

[tbrandenburg]

Motivation

• Provide visibility into harness-generated workflow log files and allow viewing recent log output from the UI.
• Standardize harness log filename format so logs can be discovered reliably by the backend.
• Surface logs alongside workspace workflows on the Tasks page so operators can inspect recent activity and errors.

Description

• Backend: added WORKFLOW_LOG_PREFIX and WORKFLOW_LOG_LOCATIONS and implemented list_workflow_logs() and read_workflow_log_tail() in cron_service.py to discover and tail workflow logs; added API endpoints GET /api/workflow-logs and GET /api/workflow-logs/{location}/{log_name} in app.py which call list_workflow_logs and read_workflow_log_tail respectively and map errors to appropriate HTTP responses.
• Frontend: added WorkflowLogSummary and WorkflowLogTail types and API wrappers getWorkflowLogs and getWorkflowLogTail in useApi.ts; updated TasksPage.tsx to fetch logs together with workspace workflows, render an "Available workflow logs" table showing filename, path, modified date and size, and open a modal showing a tailed view via openLogTail; added formatBytes helper and modal state/logic.
• UI/CSS: added .workflow-log-tail rules in page.css for better log display.
• Template: updated WORKFLOW_TO_HARNESS_PROMPT_TEMPLATE.md to require made-[workflow-name]-[timestamp]-[PID].log filenames and adjusted preferred log locations.

Testing

• Added unit tests TestWorkflowEndpoints::test_workflow_logs_success and TestWorkflowEndpoints::test_workflow_log_tail_success in packages/pybackend/tests/unit/test_api.py which mock list_workflow_logs and read_workflow_log_tail and verify the API responses; these tests passed.
• Existing workspace workflow endpoint test test_workspace_workflows_success continued to run as part of the same test file and passed.

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Codex Task

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Project	Deployment	Actions	Updated (UTC)
made	Ready	Preview, Comment	Mar 25, 2026 6:29pm