Migrate Kanban Manager App from canvas-apps into extensions/apps

[neubig]

Goal

Transfer only the existing Kanban Manager App into apps/kanban-manager/, using the Apps catalog conventions from #530. Do not migrate Conversation Trace, Artifact Handoff, or other canvas-apps applications in this PR.

Merge prerequisite (stacked implementation authorized): #530

Scope and source

Use the merged OpenHands/canvas-apps/main Kanban Manager package as the migration baseline, recording the exact source commit and preserving license/attribution. Preserve behavior, app identity, and persistent-data identity. Update installation coordinates, package-relative build paths, catalog registration and tests as needed.

Related, not silently included: OpenHands/canvas-apps#21 is an OPEN FastAPI/SQLite sidecar rewrite by Robert Brennan. Do not treat that unmerged branch as released or import its machine-specific gateway configuration. If it merges before migration begins, reassess the source commit and document what moved. Otherwise explicitly document the pending rewrite so it can later be ported to the new package rather than lost. This issue does not authorize deploying or migrating any live Kanban database.

Acceptance Criteria

• One self-contained apps/kanban-manager/ package, valid manifest and checked-in ESM entrypoint, is discoverable through Add an apps/ catalog for Agent Canvas Apps #530 catalog mechanisms.
• Source provenance and license are preserved; builds/tests operate from the new directory and published installation coordinates are correct.
• Existing app name, storage namespaces and data paths remain compatible. No user records, credentials, runtime databases, or private deployment files enter the repository.
• Existing source tests, bundle validation and real Chromium Blob smoke pass. A real isolated Canvas install/enable/open/reload/disable/re-enable walkthrough confirms board rendering and primary interactions; report any unavailable integrations honestly.
• README documents migration for existing installations without automatic service/data deletion or duplicate app identities; explicitly describes the status of sidecar PR Add marketplace.json for Claude Code plugin marketplace #21 and any deployment-specific prerequisites.
• No source deletion or edits in canvas-apps, no broad app migrations and no new host/backend APIs in this PR. Source retirement can be a separate explicitly approved change after the destination is usable.
• CI is green and one PR closes this issue; no merge or release tag without approval.

Implementation begins only after oss-agent-canvas issue triage applies ready-for-dev. Dependent PRs can stack on tested #530 implementation, but cannot merge before it.

This issue was created by an AI agent (OpenHands) on behalf of Graham Neubig.

Maintainer authorization for stacked implementation

Graham Neubig explicitly authorized stacked implementation before prerequisite issues close. Dependencies above are merge-order constraints, not closed-issue requirements for implementation readiness. Please evaluate scope readiness independently; do not close prerequisite issues or waive validation. Use native GitHub stacks for same-repository PR chains and explicit links for cross-repository dependencies.

This update was made by an AI agent (OpenHands) on behalf of Graham Neubig.