feat(tracker): spawn sessions from eligible issues

[anirudh5harma]

Summary

Issue intake can now start real worker sessions from a project's configured tracker backlog. Projects opt in with explicit eligibility rules, the daemon polls eligible open issues, and each issue gets at most one linked worker session even across daemon restarts.

The first phase is deliberately read-only toward the tracker: it does not post comments, change issue state, receive webhooks, or introduce broader provider policy. It also restores the minimal frontend verification plumbing needed to run the documented local gates on this branch.

Closes #422

Design Notes

• Intake is configured through project.config.trackerIntake and stays disabled by default.
• Duplicate prevention uses the existing durable sessions.issue_id field instead of a parallel task table.
• Worker prompts are built from normalized issue title, body, URL, labels, and assignees.
• Provider/API/spawn failures are logged per project or issue and do not stop the daemon loop.

Validation

• npm run api
• npm run lint
• cd backend && go test ./...
• cd backend && go test -race ./...
• cd backend && go vet ./...
• npm run frontend:typecheck
• npm --prefix frontend test -- --run
• npm --prefix frontend run build
• git diff --check

[anirudh5harma]

Closing this for now so the branch can go through local/peer review before opening a PR.

[anirudh5harma]

This closed duplicate was not ported as a separate PR. Its clean replacement is AgentWrapper/agent-orchestrator#2288, tracked by AgentWrapper/agent-orchestrator#2282.