[IMP-243] Migrate task-explorer (previously task-viewer) to typescript-libs

[ctuncay]

Extracts the task-viewer app from virtual-agent into this repo as a standalone task-explorer package.

What's included

New package: task-explorer/

• Full-stack app (Express backend + React/Vite frontend) for browsing and inspecting task actions and workflows
• Backend reads exclusively via @ambarltd/tasks/explorer — no direct Store queries
• Frontend: paginated task list, task detail view, Gantt chart for workflow subtasks, stats widget, auth, timezone selector, auto-refresh

Changes to @ambarltd/tasks (landed in PR #45, surfaced here via the simplification commit):

• Added excludeColumns?: string[] to all 4 explorer query functions (listTasks, searchTasks, listSubtasks, listTasksInTimeRange)
• Summary schemas (TaskActionSummary, TaskWorkflowSummary) live in explorer.ts — eliminates ~400 lines of forked query code that task-explorer previously carried locally

CI/CD

• .github/workflows/ambar-task-explorer.yaml: runs backend typecheck + unit tests and frontend typecheck + Vitest on every PR; builds and pushes ghcr.io/ambarltd/task-explorer:latest + :<sha> on merge
  to main

Test coverage

• 17 backend unit tests (decoders, API schema encoders, environment, stats requirements)
• 64 frontend tests (API client, task utils, format utils, stats utils, auth, components)

Potential future work

• PR (virtual-agent):
  • Consume @ambarltd/tasks, delete local lib/tasks/ and lib/postgres.ts — unblocked now that @ambarltd/tasks@0.1.0 is published
  • Replace task-viewer/ with image: ghcr.io/ambarltd/task-explorer:latest in docker-compose

[linear]

IMP-243 [Tasks] Move task-viewer to typescript-libs

Let's make it one of the libraries we have there alongside core.

It should be separate from the tasks library as it is not a requirement for using the tasks library.

We need

• A GitHub action that is only triggered when files for this library are changed.
• A good way to distribute the Docker image. Ideally something private and easy to set up, similar to the GitHub registry for npm, but for Docker.

[chatgpt-codex-connector]

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[lazamar]