skillscript-runtime v0.31.1

Upgrade impact: none (additive). A robustness fix + doc clarification; no breaking change.

• Fix: skill descriptions no longer go blank on a custom SkillStore. The bundled stores extract # Description: from the body and populate SkillMeta.description; a custom store that doesn't (e.g. an AMP-backed connector) left the dashboard showing a blank description in the drill-down and the wrong first-prose line (the output template) in the list. The runtime now derives description from the skill's frontmatter itself — it already has the source — whenever a store returns none. Applied in both skill_preflight (detail) and buildSkillCatalog / skill_list (list): description precedence is store-metadata → parsed # Description: → first-prose heuristic. Any custom SkillStore now shows correct descriptions without having to replicate the extraction.
• Docs: the SkillStore contract now spells out which SkillMeta fields are runtime-derivable. connector-contract-reference.md gains a convention note — body-projection metadata (description, vars) the runtime derives; substrate-only metadata (author, version, timestamps, status) your impl must return. Previously only author was documented, so the description expectation was implicit — the gap that let a connector miss it.