Add prescan data preparation to duplicate-issue-detector and stale-issues

[Copilot]

This PR adds a prescan-first data preparation flow to issue-investigation workflows so the agent starts from concrete candidates before broader search.

duplicate-issue-detector

• Added a Prescan issue index step that writes /tmp/gh-aw/agent/issues-index.tsv with issue number, title, and state.
• Prescan collects the newest 500 and oldest 500 issues, then de-duplicates by issue number.
• In .github/workflows/gh-aw-duplicate-issue-detector.md, added bash: true and updated the prompt flow to include Step 2: Scan the Issue Index before targeted search and candidate evaluation (with step renumbering through post result).
• Added github/workflows/gh-aw-duplicate-issue-detector.md with the same prescan-first investigation structure for the workflow-source copy.

stale-issues

• Added a Prescan open issues step that writes /tmp/gh-aw/agent/open-issues.tsv with number, title, updated_at, created_at, and label_names.
• In both .github/workflows/gh-aw-stale-issues.md and github/workflows/gh-aw-stale-issues.md, prescan now fetches up to 500 open issues sorted by least recently updated.
• Added bash: true and updated the prompt flow to include Step 0 so the agent reads the prescanned index first and prioritizes oldest updated_at candidates.

Workflow source and docs updates

• Added workflow source copies under github/workflows/ for both gh-aw-duplicate-issue-detector.md and gh-aw-stale-issues.md with the prescan-first investigation structure.
• Regenerated both .lock.yml compiled workflows to include the prescan steps and prompt updates.
• Updated workflow READMEs for both duplicate-issue-detector and stale-issues to document the prescan-first investigation flow.

Notes

• This follows the same prescan-first pattern used by estc-actions-resource-not-accessible-detector.
• Fixes Identify workflows we should prepare data for #479

Generated by Update PR Body for issue #481

[coderabbitai]

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📝 Walkthrough

Walkthrough

This PR adds prescan steps and documentation for two GitHub Actions workflows. The duplicate-issue-detector workflow now creates an issue index by fetching the newest 500 and oldest 500 issues, deduplicating them, and writing a TSV index used as the initial scan input. The stale-issues workflow now prescans up to 500 open issues (sorted by least-recently-updated) into a TSV to seed the candidate pool. README and workflow docs/lock files were updated to describe the index-driven prescan flow and to adjust step numbering and labels.

Possibly related PRs

• fix(duplicate-issue-detector): improve comment formatting for related vs duplicate issues #340: Modifies the duplicate-issue-detector workflow files and adjusts step headings and post-result/comment formatting, touching the same workflow/config surfaces updated here.
• switch to upstream compiler, rename workflows, update fragments #312: Updates duplicate-issue-detector and stale-issues workflow files and READMEs; shares code-level overlap with the prescan/index changes added in this PR.

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	PR implements prescan data preparation for duplicate-issue-detector and stale-issues workflows, enabling agents to start with concrete candidate pools [#479].
Out of Scope Changes check	✅ Passed	All changes directly align with PR objectives: prescan steps for duplicate-issue-detector and stale-issues, updated documentation, and workflow copies.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch copilot/investigate-prep-workflows

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[strawgate]

/ai aren't file read tools included by default? Is enabling bash here a bad idea? Please investigate.

Let's make sure we have logic to not grab overlapping issues for duplicate issues and for stale issues let's grab like 500 issues

Please update the pr

[cla-checker-service]

❌ Author of the following commits did not sign a Contributor Agreement:
, , df76679

Please, read and sign the above mentioned agreement if you want to contribute to this project

[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In @.github/workflows/gh-aw-stale-issues.md:
- Around line 115-117: The fenced code block containing the command "cat
/tmp/gh-aw/agent/open-issues.tsv" is missing a language tag; update the opening
fence from ``` to ```bash so the block declares the language (e.g., change the
snippet around the "cat /tmp/gh-aw/agent/open-issues.tsv" command to start with
```bash).
- Around line 92-97: The command invoking gh issue list currently swallows all
errors via "2>/dev/null || true", which hides prescan failures and allows the
workflow to continue with an empty "$issues_file"; remove the silent suppression
and let failures surface by deleting the "2>/dev/null || true" tail (or replace
it with explicit error handling that writes stderr to logs and exits non‑zero),
so that the gh issue list invocation fails the job on error and preserves
visibility into problems when populating "$issues_file".

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ℹ️ Review info

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between ea641b3 and 0db1c5c.

📒 Files selected for processing (2)

• .github/workflows/gh-aw-stale-issues.lock.yml
• .github/workflows/gh-aw-stale-issues.md

[github-actions]

Requesting changes due to a verified prescan error-handling gap that can silently degrade duplicate detection quality.

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