feat(skill-template): add bracket placeholder for license field

[KemingHe]

Related

• One instance of Copilot review flagged name: [skill-name] as invalid YAML sequence

Problem

In agent-skills/skill-creation/assets/skill-template.md, the license field uses a bare literal value (MIT) while other placeholder fields like name and description use square bracket notation ([skill-name], [One-line summary...]). This is inconsistent -- the license field should also signal to the AI that it needs to be filled in per-project rather than assumed as MIT.

Copilot also flagged name: [skill-name] as an invalid YAML sequence. This is a known non-issue: the template is consumed by AI agents for drafting, not parsed directly as YAML. The bracket convention is intentional and should be preserved for all placeholder fields.

Proposed Solution

• Change license: MIT to license: [license] in skill-template.md
• Keep all existing bracket placeholders as-is (including name: [skill-name])
• Optionally add a comment in the template noting that bracket placeholders are intentional and not meant to be valid YAML

Alternatives Considered

• Quoting bracket placeholders (e.g. name: "[skill-name]") to satisfy YAML parsers - rejected; adds noise and the template is AI-consumed, not directly parsed
• Leaving license: MIT as a sensible default - rejected; not all downstream repos use MIT, the template should not assume a license