v0.3.0 — input contracts + durable steps

Workflow input contracts — meta.argsSchema

A workflow module can now declare a JSON Schema for its --args:

export const meta = {
  argsSchema: {
    type: 'object',
    required: ['target'],
    properties: { target: { type: 'string', minLength: 1 } },
    additionalProperties: false,
  },
}

• Validates the effective args verbatim at admission time, on fresh runs and resumes alike — a violation terminates the run before any agent or step executes.
• Failures always produce full terminal artifacts (journal end record, result.json, no agent events) — including malformed schemas, unsupported keywords, and validator throws. Nothing escapes as a bare crash.
• The validator's supported subset (type, required, properties, additionalProperties: false, items, enum, const, min/max bounds, anyOf) rejects anything it doesn't enforce loudly — no silently ignored constraints.

Durable side-effect nodes — step(name, args?, fn)

Journaled local work (git commands, file writes, API calls) with replay-on-resume:

const sha = await step('commit', { msg }, async () => {
  await exec(`git commit -m "${msg}"`)
  return exec('git rev-parse HEAD')
})

• A completed callback's JSON result is journaled and replayed on resume without re-executing; failed or crash-window (start-only) attempts re-run.
• The contract is durable memoization, not exactly-once — callbacks should be idempotent or carry idempotency keys.
• Steps use an independent per-branch counter and a separate key domain, so adding or removing a step() never shifts agent resume keys (existing journals stay resumable; key version unchanged).
• The completed journal record seals the outcome: telemetry failures after completion can never cause a re-run.
• Strict JSON normalization for args/results: undefined, functions, BigInt, NaN, cycles, and sparse arrays are rejected loudly; -0 normalizes to 0; a void callback resolves to null.

Observability

Steps are first-class everywhere: CLI status/tail, the MCP surface, and the web viewer cockpit (step lifecycle, replay markers, failures, durations).

Docs

New examples/durable-steps.workflow.js, plus README, guide, architecture, skill, and TypeScript declaration updates for both features.