[SE-3-03] Add stale issue detector workflow

[Copilot]

Implements automated stale issue management scoped to docs-v2 issues, marking inactive issues and closing them if unaddressed.

Description

Adds actions/stale@v9-based workflow that marks docs-v2 issues stale after 60 days of inactivity and auto-closes them after 14 more days. Exempt labels (pinned, critical/high priority, in-progress, needs-triage, needs-info) prevent false positives. The rolling docs-v2 index issue is pinned on creation to avoid being swept.

Scope

In scope:

• .github/workflows/stale-issue-detector.yml — new workflow
• .github/workflows/issue-auto-label.yml — new label metadata entries
• .github/workflows/docs-v2-issue-indexer.yml — pin index issue on creation
• v2/resources/documentation-guide/automations-workflows.mdx — English docs
• v2/es/resources/documentation-guide/automations-workflows.mdx — Spanish docs

Out of scope: All other workflows, content pages, label logic beyond metadata registration.

Validation

• actions/stale@v9 — no known CVEs (Advisory DB checked)
• CodeQL scan: 0 alerts
• Workflow YAML linted via GitHub Actions parser conventions
• Label metadata verified consistent with existing ensureLabel patterns in issue-auto-label.yml

Follow-up Tasks

• Manually add status: pinned to any pre-existing index issues that were created before this change
• Consider tuning days-before-issue-stale (currently 60) after first month of operation

Type of Change

• Bug fix (fixes an issue)
• New content (adds new documentation)
• Content update (improves existing content)
• Style/formatting fix
• Information architecture change
• Other (please describe)

New CI/CD automation workflow + supporting label definitions + documentation.

Related Issues

Related to #

Changes Made

• .github/workflows/stale-issue-detector.yml — daily (03:00 UTC) + workflow_dispatch; only-labels: docs-v2; stale at 60d, close at +14d; PRs excluded (days-before-pr-stale: -1); capped at 30 ops/run
• .github/workflows/issue-auto-label.yml — registers status: pinned, status: stale, status: autoclosed in labelMeta so ensureLabel creates them with correct colors/descriptions
• .github/workflows/docs-v2-issue-indexer.yml — adds status: pinned to index issue labels on creation, making it exempt from stale detection
• Docs (EN + ES) — adds Stale Issue Detector section after Docs v2 Issue Indexer, following existing section conventions

Testing

• Tested locally with npm run dev
• Verified all links work
• Checked formatting and style
• Reviewed against style guides
• Screenshots (if UI changes)

Screenshots (if applicable)

N/A — no UI changes.

Checklist

• My changes follow the style guides
• I've reviewed the Component Library for available components
• I've updated related pages if needed
• I've checked for broken links
• My changes are clear and easy to understand
• I've tested locally
• I've added/updated keywords and metadata if needed

Additional Notes

exempt-issue-labels covers all labels that signal active triage or high urgency. Removing status: stale from any issue resets its timer without any workflow changes needed.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[SE-3-03] Stale issue detector</issue_title>
<issue_description>Tracking issue for SE-3-03 in the Sprint 3 + Post-Migration Audit stream.

Scope:

• Implement Stale issue detector
• Keep changes isolated to the task branch/worktree
• Validate against docs-v2 governance rules before PR</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [SE-3-03] Stale issue detector #799

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