[product-manager-impersonator] Deduplicate `[aw] No-Op Runs` trackers via maintenance operation

## Feature Idea

**Summary:** Add a new `agentics-maintenance` operation that keeps exactly one open `[aw] No-Op Runs` tracker issue per repository.

## Why a Customer Would Want This
Repositories running many scheduled agents rely on no-op tracking for transparency, but duplicate open `[aw] No-Op Runs` issues fragment history and create operator noise. A single canonical tracker keeps signal clean without losing data.

## Rough Implementation Sketch
- Extend `.github/workflows/agentics-maintenance.yml` `operation` options with a new mode (for example, `dedupe_noop_runs`).
- Add a dedicated job for that mode that finds open issues titled `[aw] No-Op Runs`, keeps one canonical issue, and comments/closes the extras with a link to the canonical thread.
- Preserve current default behavior (no change unless this maintenance operation is explicitly run).
- Document the operation in `docs/workflows/gh-agent-workflows.md` alongside `safe_outputs` and `create_labels`.

## Why It Won't Be That Hard
`agentics-maintenance` already implements explicit maintenance operations and issue lifecycle actions, so this is an additive operation in an existing control plane rather than a new system.

## Evidence
- Existing maintenance operation plumbing already supports explicit dispatch modes: `.github/workflows/agentics-maintenance.yml` (operation inputs and operation-specific jobs).
- Current docs list only `safe_outputs` and `create_labels` as manual operations, leaving room for this operational hygiene action: `docs/workflows/gh-agent-workflows.md`.
- Duplicate open trackers exist right now: #1039, #1037, and #945 (all titled `[aw] No-Op Runs`).
- Related but different request already exists: #935 (toggle whether no-ops are reported as issues); this proposal keeps reporting enabled but deduplicates trackers.

> [!NOTE]
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> 🔒 Integrity filter blocked 57 items
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> The following items were blocked because they don't meet the GitHub integrity level.
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> - [#1128](https://github.com/elastic/ai-github-actions/pull/1128) `search_pull_requests`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#359](https://github.com/elastic/ai-github-actions/issues/359) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#1067](https://github.com/elastic/ai-github-actions/issues/1067) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#168](https://github.com/elastic/ai-github-actions/issues/168) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#117](https://github.com/elastic/ai-github-actions/issues/117) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#593](https://github.com/elastic/ai-github-actions/issues/593) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#276](https://github.com/elastic/ai-github-actions/issues/276) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#575](https://github.com/elastic/ai-github-actions/issues/575) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#182](https://github.com/elastic/ai-github-actions/issues/182) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#59](https://github.com/elastic/ai-github-actions/issues/59) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#119](https://github.com/elastic/ai-github-actions/issues/119) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#140](https://github.com/elastic/ai-github-actions/issues/140) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#432](https://github.com/elastic/ai-github-actions/issues/432) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#457](https://github.com/elastic/ai-github-actions/issues/457) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#424](https://github.com/elastic/ai-github-actions/issues/424) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#333](https://github.com/elastic/ai-github-actions/issues/333) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - ... and 41 more items
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> To allow these resources, lower `min-integrity` in your GitHub frontmatter:
>
> ```yaml
> tools:
> github:
> min-integrity: approved # merged | approved | unapproved | none
> ```
>
>

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