docs: add qmd reference page to fix broken links in docs build (#24999)

Author: Copilot

docs/src/content/docs/reference/qmd.md

@@ -0,0 +1,125 @@
+---
+title: QMD Documentation Search
+description: Configure vector similarity search over documentation files using the qmd tool in agentic workflows.
+sidebar:
+  order: 820
+---
+
+QMD Documentation Search provides vector similarity search over documentation files. It runs [tobi/qmd](https://github.com/tobi/qmd) as an MCP server so agents can find relevant documentation by natural language query.
+
+The search index is built in a dedicated indexing job (which has `contents: read`) and shared with the agent job via GitHub Actions cache, so the agent job does not need `contents: read` permission.
+
+:::caution[Experimental]
+QMD Documentation Search is an experimental feature. The API may change in future releases.
+:::
+
+## Basic Configuration
+
+```aw wrap
+---
+tools:
+  qmd:
+    checkouts:
+      - pattern: "docs/**/*.md"
+---
+```
+
+## Configuration Options
+
+### `checkouts`
+
+A list of named documentation collections built from checked-out repositories. Each entry specifies which files to index from the current repository or a different repository.
+
+```aw wrap
+---
+tools:
+  qmd:
+    checkouts:
+      - pattern: "docs/**/*.md"
+      - pattern: "README.md"
+---
+```
+
+Each checkout entry can optionally specify its own checkout configuration to target a different repository.
+
+### `searches`
+
+A list of GitHub code search queries whose results are downloaded and added to the qmd index.
+
+```aw wrap
+---
+tools:
+  qmd:
+    searches:
+      - query: "repo:github/gh-aw language:markdown"
+---
+```
+
+### `cache-key`
+
+A GitHub Actions cache key used to persist the qmd index across workflow runs. When set without any indexing sources (`checkouts`/`searches`), qmd operates in read-only mode: the index is restored from cache and all indexing steps are skipped.
+
+```aw wrap
+---
+tools:
+  qmd:
+    cache-key: "qmd-docs-${{ github.repository }}"
+---
+```
+
+### `gpu`
+
+Enable GPU acceleration for the embedding model (`node-llama-cpp`). Defaults to `false`: `NODE_LLAMA_CPP_GPU=false` is injected into the indexing step so GPU probing is skipped on CPU-only runners. Set to `true` only when the indexing runner has a GPU.
+
+```aw wrap
+---
+tools:
+  qmd:
+    gpu: true
+    runs-on: gpu-runner
+---
+```
+
+### `runs-on`
+
+Override the runner image for the qmd indexing job. Defaults to the same runner as the agent job. Use this when the indexing job requires a different runner (e.g. a GPU runner).
+
+```aw wrap
+---
+tools:
+  qmd:
+    runs-on: ubuntu-latest
+---
+```
+
+## Example: Index Documentation from Multiple Sources
+
+```aw wrap
+---
+tools:
+  qmd:
+    checkouts:
+      - pattern: "docs/**/*.md"
+      - pattern: "*.md"
+    cache-key: "qmd-docs-${{ github.repository }}-${{ github.run_id }}"
+---
+```
+
+## Example: Read-Only Mode with Pre-Built Index
+
+```aw wrap
+---
+tools:
+  qmd:
+    cache-key: "qmd-docs-my-project"
+---
+```
+
+In read-only mode, the index is restored from cache and no indexing steps are run. This is useful when the index is built separately and shared across workflows.
+
+## Related Documentation
+
+- [Tools](/gh-aw/reference/tools/) - Overview of all available tools and configuration
+- [Frontmatter](/gh-aw/reference/frontmatter/) - Complete frontmatter configuration guide
+- [Cache Memory](/gh-aw/reference/cache-memory/) - Persistent memory across workflow runs
+- [GitHub Tools](/gh-aw/reference/github-tools/) - GitHub API operations