chore: version 0.3.0

[miinhho]

Summary

Bumps package.json to 0.3.0 and rewrites the README for a first-time reader.

Why 0.3.0

npm's 0.2.1 predates #22. Since then:

• refactor: single-result Job plus HandoffJob for one-shot handoff #22 — breaking: Job<Result> is a single-result lifetime; Published, the publisher body argument, JobPublisher, and Job.value() are removed; HandoffJob models the one-shot handoff.
• perf: link an external cancellation source lazily, on first observation #24, perf: create the AbortController, drain, and binding Map only when used #26 — no public behavior change (lazy external-signal link; lazy AbortController, conditional drain, single-binding frames; Cancellation component).

Pre-1.0, a breaking change is a minor bump.

README

Same contracts, reorganized so it reads front to back:

• opens with the model in one paragraph and a runnable example that shows the two properties that matter (settles after the subtree; a failing child cancels siblings)
• Jobs split into ownership / lifecycle / observing the result / failure instead of one ten-bullet list
• cancellation and deadlines before context, since signal() appears in every example
• Supervisor and TaskGroup each state what they are, then their policies
• HandoffJob last, introduced by the problem it solves
• an API summary table at the end
• terms (owner, seed, admission, boundary) are defined where they first appear

Verification

• pnpm format, pnpm check, pnpm build, pnpm test (131), pnpm pack → tiberjs-runner-0.3.0.tgz

After merge: dispatch publish.yml from main, then drop the packed-runner overrides in server, transports, and manager and regenerate their lockfiles against ^0.3.0.