Add duplicate resource detector agentic workflow

Weekly scheduled workflow that scans agents, prompts, instructions, and
skills for potential duplicates based on name, description, and content
similarity. Reports findings as a GitHub issue with task list checkboxes
for review. Checks previous duplicate-review issues to exclude known
accepted pairs.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/duplicate-resource-detector.md

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+---
+description: Weekly scan of agents, prompts, instructions, and skills to identify potential duplicate resources and report them for review
+on:
+  schedule: weekly
+permissions:
+  contents: read
+  issues: read
+tools:
+  github:
+    toolsets: [repos, issues]
+safe-outputs:
+  create-issue:
+    max: 1
+    close-older-issues: true
+    labels:
+      - duplicate-review
+  noop:
+---
+
+# Duplicate Resource Detector
+
+You are an AI agent that audits the resources in this repository to find potential duplicates — resources that appear to serve the same or very similar purpose.
+
+## Your Task
+
+Scan all resources in the following directories and identify groups of resources that may be duplicates or near-duplicates based on their **name**, **description**, and **content**:
+
+- `agents/` (`.agent.md` files)
+- `prompts/` (`.prompt.md` files)
+- `instructions/` (`.instructions.md` files)
+- `skills/` (folders — check `SKILL.md` inside each)
+
+### Step 1: Gather Resource Metadata
+
+For each resource, extract:
+
+1. **File name** (the path)
+2. **Front matter `description`** field
+3. **Front matter `name`** field (if present)
+4. **First ~20 lines of body content** (the markdown after the front matter)
+
+Use bash to read files efficiently. For skills, read `skills/<name>/SKILL.md`.
+
+### Step 2: Identify Potential Duplicates
+
+Compare resources and flag groups that look like potential duplicates. Consider resources as potential duplicates when they share **two or more** of the following signals:
+
+- **Similar names** — file names or `name` fields that share key terms (e.g., `react-testing.prompt.md` and `react-unit-testing.prompt.md`)
+- **Similar descriptions** — descriptions that describe the same task, technology, or domain with only minor wording differences
+- **Overlapping scope** — resources that target the same language/framework/tool and the same activity (e.g., two separate "Python best practices" instructions)
+- **Cross-type overlap** — an agent and a prompt (or instruction and agent) that cover the same topic so thoroughly that one may make the other redundant
+
+Be pragmatic. Resources that cover related but distinct topics are NOT duplicates. For example:
+- `react.instructions.md` (general React coding standards) and `react-testing.prompt.md` (React testing prompts) are **not** duplicates — they serve different purposes.
+- `python-fastapi.instructions.md` and `python-flask.instructions.md` are **not** duplicates — they target different frameworks.
+- `code-review.agent.md` and `code-review.prompt.md` that both do the same style of code review **are** potential duplicates worth flagging.
+
+### Step 3: Check for Known Accepted Duplicates
+
+Before finalizing the report, search for **previous issues** labeled `duplicate-review` in this repository:
+
+```
+Search for issues with label "duplicate-review" that are closed
+```
+
+Read the comments and body of those past issues to find any pairs or groups that reviewers have explicitly marked as **"accepted"** or **"not duplicates"**. Look for phrases like:
+- "accepted as-is"
+- "not duplicates"
+- "intentionally separate"
+- "keep both"
+- checked task list items (i.e., `- [x]`)
+
+Exclude those known-accepted pairs from the current report. If you include a group that was previously reviewed, add a note: `(previously reviewed — see #<issue-number>)`.
+
+### Step 4: Produce the Report
+
+Create an issue titled: `🔍 Duplicate Resource Review`
+
+Format the body as follows:
+
+```markdown
+### Summary
+
+- **Potential duplicate groups found:** N
+- **Resources involved:** M
+- **Known accepted (excluded):** K pairs from previous reviews
+
+### How to Use This Report
+
+Review each group below. If the resources are intentionally separate, check the box to mark them as accepted. These will be excluded from future reports.
+
+### Potential Duplicates
+
+#### Group 1: <Short description of what they share>
+
+- [ ] Reviewed — these are intentionally separate
+
+| Resource | Type | Description |
+|----------|------|-------------|
+| `agents/foo.agent.md` | Agent | Does X for Y |
+| `prompts/foo.prompt.md` | Prompt | Also does X for Y |
+
+**Why flagged:** <Brief explanation of the similarity>
+
+---
+
+#### Group 2: ...
+
+<repeat for each group>
+```
+
+Use `<details>` blocks to collapse groups if there are more than 10.
+
+### Safe Output Guidance
+
+- If you find potential duplicates: use `create-issue` to file the report.
+- If **no** potential duplicates are found (after excluding known accepted ones): call `noop` with the message: "No potential duplicate resources detected. All resources appear to serve distinct purposes."
+
+## Guidelines
+
+- Be conservative — only flag resources where there is a genuine risk of redundancy.
+- Group related duplicates together (don't list the same pair twice in separate groups).
+- Sort groups by confidence (strongest duplicate signals first).
+- Include cross-type duplicates (e.g., an agent and a prompt doing the same thing).
+- Limit the report to the top 20 most likely duplicate groups to keep it actionable.
+- For skills, use the folder name and description from `SKILL.md`.
+- Process resources in batches to stay within time limits — prioritize name and description comparison, then spot-check content for top candidates.