Skillscript

Upgrade impact: none (additive). New help() topic + expanded server instructions; no behavior change.

• New help({topic: "error-handling"}) topic — the "how do I keep one call from aborting the whole skill" playbook, now reachable through the tool-help surface an agent author actually uses (not just the language-ref doc, which agents authoring via MCP never read). Covers the four containment primitives — the (fallback: "…") op trailer (the per-call opt-out), the ${REF|fallback:"x"} pipe filter, the else: block, and # OnError: — plus the five-rule discipline (fallback every fallible op; fallback each fan-out leg or one failure sinks the rest; |fallback position-independence; output-template var safety; degrade loud, not silent). Content mirrors the language-ref "Robustness & error containment" section so the two stay in sync.
• Discoverability wiring: error-handling added to available_topics, the help tool description's topic list, and the unknown-topic message; the no-arg quickstart now names the (fallback:) primitive and points to the topic; the MCP server instructions (shown to every agent at session start) gained a one-line robustness note. So an agent meets the containment guidance passively (server instructions), on demand (help), and at the quickstart — the surfaces it uses, rather than the docs it doesn't.