Update issue card closed-state labels from GitHub state reasons

[Copilot]

Description:

Issue cards only exposed open / closed, which lost the distinction between completed work and non-actionable closures. This updates the issue preview header to reflect GitHub's closed issue reasons directly in the card UX.

• Status mapping

  • Map closed issue state_reason to the card subtitle and icon:
    • completed → 🟣 completed
    • not_planned → ⊘ not planned
    • duplicate → ⊘ duplicate
  • Keep existing behavior for open issues and closed issues without a reason.
  • Update the non-actionable closed-state icons based on review feedback.

• Type support

  • Extend GitHubIssue with optional state_reason so the UI can render the richer closed-state variants.

• Coverage

  • Add focused unit tests for completed, not planned, and duplicate issue cards, including the reviewed ⊘ icon expectations.

if (data.state === "closed") {
  switch (data.state_reason) {
    case "completed":
      stateIcon = "🟣";
      stateText = "completed";
      break;
    case "not_planned":
      stateIcon = "⊘";
      stateText = "not planned";
      break;
    case "duplicate":
      stateIcon = "⊘";
      stateText = "duplicate";
      break;
  }
}

Related Issues:

• [feature] Update issue status UX

Checklist:

• Review the CONTRIBUTING.md documentation.
• Add a reference to a related issue in the repository.
• Add a description of the changes proposed in the pull request.
• Add unit tests if applicable.
• Update documentation if applicable.
• Add a note in the CHANGELOG.md if applicable.

[ianlewis]

@copilot please address these comments

[ianlewis]

Suggested change

	stateIcon = "⚪";
	stateIcon = "⊘";

[ianlewis]

Suggested change

	stateIcon = "⚪";
	stateIcon = "⊘";

[Copilot]

@copilot please address these comments

Addressed in 89761df.