feat: Introduce workflow level concurrency

[octoper]

Summary

This PR adds workflow-level concurrency, It introduces input-based concurrency buckets (similar to Inngest-style concurrency) so runs can be constrained by a resolved key/limit at enqueue time, while still working alongside worker-slot concurrency.

Motivation

Worker concurrency limits total in-flight runs per worker, but we also need per-workflow/per-tenant style limits (eg. tenant:acme max 1 or max N active runs), resolved from validated workflow input and enforced centrally in the backend.

Disclaimer
this is just a quick shot on the workflow level concurrency coded mainly by AI and small intervention by me, I want to first use it in a project to make sure everything works as expected and adjust it or scrape it off completely 😅

[Copilot]

Pull request overview

Adds workflow-level concurrency to OpenWorkflow by persisting a resolved (concurrencyKey, concurrencyLimit) on each run at enqueue time and enforcing bucket capacity during backend claim/dequeue, alongside existing worker-slot concurrency.

Changes:

• Extend workflow specs with optional concurrency (static or input-derived key/limit) and resolve/validate it in the client before creating a run.
• Persist concurrency_key / concurrency_limit in SQLite/Postgres via migrations + indexes, and enforce limits during claimWorkflowRun.
• Add backend/worker/client tests plus user-facing documentation (README + docs + architecture notes).

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
packages/openworkflow/workflow.ts	Adds workflow spec concurrency types/config.
packages/openworkflow/index.ts	Re-exports new concurrency types.
packages/openworkflow/core/workflow.ts	Adds persisted concurrency fields to WorkflowRun.
packages/openworkflow/backend.ts	Extends CreateWorkflowRunParams with concurrency metadata.
packages/openworkflow/client.ts	Resolves + validates concurrency at enqueue time and persists it on runs.
packages/openworkflow/sqlite/sqlite.ts	SQLite migration adds concurrency columns + index.
packages/openworkflow/sqlite/backend.ts	Persists concurrency metadata; enforces limit in claim query; adds normalization helper.
packages/openworkflow/postgres/postgres.ts	Postgres migration adds concurrency columns + index.
packages/openworkflow/postgres/backend.ts	Persists concurrency metadata; enforces limit in claim query; adds normalization helper.
packages/openworkflow/backend.testsuite.ts	Adds cross-backend tests for concurrency persistence + enforcement.
packages/openworkflow/worker.test.ts	Adds integration tests showing worker-slot concurrency still respects workflow concurrency.
packages/openworkflow/client.test.ts	Tests concurrency resolution/validation + enqueue failure behavior.
packages/openworkflow/sqlite/sqlite.test.ts / packages/openworkflow/postgres/postgres.test.ts	Verifies migrations create required columns + index.
packages/docs/docs/workflows.mdx / packages/docs/docs/workers.mdx / packages/openworkflow/README.md / ARCHITECTURE.md	Documents workflow concurrency behavior and scope.

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[Copilot]

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated no new comments.

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