fix(a11y): ISSUE_TEMPLATE README.md Mermaid diagram missing YAML header block `accTitle`/`accDescr`

[ashleyshaw]

Summary

The Mermaid diagram in .github/ISSUE_TEMPLATE/README.md uses the deprecated inline accTitle/accDescr syntax (declared inside the flowchart body, after the diagram-type line) rather than the canonical YAML header block format mandated by instructions/mermaid.instructions.md v2.0.

Current (broken) format

flowchart TD
    accTitle: Issue template workflow
    accDescr: Shows how users select an issue template...

Loading

Required format

---
accTitle: Issue template workflow
accDescr: Shows how users select an issue template...
---
flowchart TD

Loading

Impact

• validate:mermaid-accessibility CI check flags diagrams that do not carry the YAML header block
• Screen readers may not surface the accessible title/description for this diagram
• Inconsistency with all other diagrams in the repository which were updated to YAML block format in the Wave-5 Mermaid WCAG sweep

Acceptance Criteria

• .github/ISSUE_TEMPLATE/README.md diagram uses the YAML header block (--- delimiters before the diagram type line) for accTitle and accDescr
• validate:mermaid-accessibility passes
• Frontmatter version and last_updated bumped per convention

Related

• instructions/mermaid.instructions.md v2.0 — canonical diagram standards
• Wave-5 Mermaid WCAG sweep (PR feat(mermaid): WCAG 2.2 AA colour contrast validation and updated diagram standards #977, PR [codex] Mermaid diagrams WCAG 2.2 AA contrast sweep #987)

[linear-code]

LS-1102

[github-actions]

⚠️ This issue does not follow a required issue template.

Missing required section(s): Definition of Ready (DoR), Definition of Done (DoD)

The issue will remain open and flagged until the body is corrected.
Please update the issue with one of the official templates:

• https://github.com/lightspeedwp/.github/issues/new/choose

If this was opened by automation, update the automation to preserve the template sections before creating the issue.