docs: explicitly require exactly one changelog type checkbox in copilot instructions

[Copilot]

The copilot-instructions.md guidance on PR descriptions was silent on the "exactly one checkbox" constraint for the changelog type section, leaving contributors unaware that an unchecked type blocks the release workflow entirely.

Changes

• .github/copilot-instructions.md: Replaced the vague "type of change must be accurately indicated" sentence with an explicit rule — exactly one of Major/Minor/Patch must be checked, the workflow picks the first matching box (Major → Minor → Patch), and leaving all unchecked prevents release creation.

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[Copilot]

Pull request overview

Updates repository contribution guidance so PR authors understand the release workflow’s constraints around changelog type selection.

Changes:

• Clarifies that the changelog markers are required and that a changelog type checkbox must be selected.
• Adds explicit guidance about the checkbox selection rule and the workflow’s selection precedence (Major → Minor → Patch).

[Copilot]

There’s an extra leading space before “The type of change…” which makes this paragraph misaligned with the surrounding text and can cause odd Markdown rendering in some contexts. Remove the leading whitespace so the paragraph starts flush-left like the others.

Suggested change

	The type of change must be accurately indicated to ensure proper versioning. **Exactly one** of the Major/Minor/Patch checkboxes must be checked — the release workflow picks the first matching checked box (Major → Minor → Patch) and will fail to create a release if none are checked.
	The type of change must be accurately indicated to ensure proper versioning. **Exactly one** of the Major/Minor/Patch checkboxes must be checked — the release workflow picks the first matching checked box (Major → Minor → Patch) and will fail to create a release if none are checked.

[Copilot]

The sentence says “Exactly one … must be checked” but the workflow logic actually selects the first matching checkbox (Major → Minor → Patch) and only hard-fails when none are checked. To keep the docs strictly accurate, consider wording this as a contributor requirement (“check exactly one”) while also noting what happens if multiple are checked (the workflow will choose the first match).

Suggested change

	The type of change must be accurately indicated to ensure proper versioning. **Exactly one** of the Major/Minor/Patch checkboxes must be checked — the release workflow picks the first matching checked box (Major → Minor → Patch) and will fail to create a release if none are checked.
	The type of change must be accurately indicated to ensure proper versioning. Contributors must select **exactly one** of the Major/Minor/Patch checkboxes; if multiple are checked the release workflow will use the first matching checked box in priority order (Major → Minor → Patch) and will fail to create a release only if none are checked.