Add support for idempotency keys

[jamescmartinez]

Closes #121, Closes #136

Summary

This pr implements idempotency so reusing the same idempotencyKey returns the existing run (within 24h)

ow.runWorkflow(spec, input, { idempotencyKey })

Docs updated with additional info

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Copilot]

Pull request overview

Adds idempotency key support to OpenWorkflow run creation so repeated requests with the same key return the existing canonical run (per namespace + workflow), with coverage across both SQLite and PostgreSQL backends.

Changes:

• Pass idempotencyKey from OpenWorkflow.runWorkflow() / workflow.run() into backend run creation.
• Implement idempotent run creation in SQLite (transaction + lookup) and Postgres (advisory-lock + lookup) backends.
• Add backend + client test coverage and update docs/changelog/roadmap to document the feature.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/openworkflow/sqlite/backend.ts	Adds idempotent run creation logic for SQLite via transaction + lookup.
packages/openworkflow/postgres/backend.ts	Adds idempotent run creation logic for Postgres via advisory lock + lookup.
packages/openworkflow/client.ts	Wires idempotencyKey option through to backend.
packages/openworkflow/client.test.ts	Adds client-level tests verifying idempotency key persistence and dedupe behavior.
packages/openworkflow/backend.testsuite.ts	Adds cross-backend behavioral tests for idempotency semantics and concurrency.
packages/openworkflow/README.md	Updates feature list to include idempotency keys.
packages/openworkflow/CHANGELOG.md	Notes unreleased idempotency support.
packages/docs/docs/workflows.mdx	Documents optional idempotency key usage and semantics.
packages/docs/docs/roadmap.mdx	Moves idempotency keys from “Coming Soon” to completed.

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 6 comments.

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