[docs] Update Repo Mind Light image digest for 2026-06-17

## Summary

- Updated the default `image` input in `.github/workflows/shared/repo-mind-light.md` from `sha256:a30f27d60ed871e05da29c41d1707abd4cbb42e28f932a640ee79a4ed1b6c73e` to `sha256:6d159c10513f365250f46de421096f4e61cb7bb04d36e10db6b62714c523f822`.

## Source Context

- Inspected the source repository's compiled lock file (`.github/workflows/repo-mind-light-aw.lock.yml`) and pinned import (`.github/aw/imports/githubnext/repo-mind-light-aw/.../`).
- Both reference the newer digest `sha256:6d159c10...` consistently across all three usage sites in the lock file.
- The previous digest `sha256:a30f27d6...` predates source version v0.10.0/v0.10.1, which includes the Soma index persistence fix (`Persist indexes in store path`) and the Soma title field fix.
- The shared workflow default was out of sync: the source repo had already updated its pinned import to the newer digest but the aw repo's `main` branch still shipped the old one.

## Validation

- Confirmed the new digest appears in three places in the source lock file (prep-job image pull, agent-job MCP start, and the compiled REPO_MIND_LIGHT_IMAGE env var).
- No other documentation discrepancies were found. The README, YAML comment block, and config schema examples are all accurate.

## Notes

- No README changes are needed; the README describes the image input generically and does not pin a digest.

---

> [!WARNING]
> **Protected Files — Push Permission Denied**
>
> This was originally intended as a pull request, but the patch modifies protected files. A human must create the pull request manually.
>
>
> Protected files
>
> - [.github/workflows/shared/repo-mind-light.md](https://github.com/githubnext/repo-mind-light-aw/blob/main/.github/workflows/shared/repo-mind-light.md)
>
> The push was rejected because GitHub Actions does not have `workflows` permission to push these changes, and is never allowed to make such changes, or other authorization being used does not have this permission.
>
>

Create the pull request manually

```sh
# Download the patch from the workflow run
gh run download 27683437294 -n agent -D /tmp/agent-27683437294

# Create a new branch
git checkout -b docs/update-repo-mind-light-aw-2026-06-17-c10911adbfda2591 main

# Apply the patch (--3way handles cross-repo patches)
git am --3way /tmp/agent-27683437294/aw-githubnext-repo-mind-light-aw-docs-update-repo-mind-light-aw-2026-06-17.patch

# Push the branch and create the pull request
git push origin docs/update-repo-mind-light-aw-2026-06-17-c10911adbfda2591
gh pr create --title '[docs] Update Repo Mind Light image digest for 2026-06-17' --base main --head docs/update-repo-mind-light-aw-2026-06-17-c10911adbfda2591 --repo githubnext/repo-mind-light-aw
```

> Generated by [Repo Mind Light AW Documentation Updater](https://github.com/githubnext/repo-mind-light/actions/runs/27683437294) · ● 57.3M · [◷](https://github.com/search?q=repo%3Agithubnext%2Frepo-mind-light-aw+%22gh-aw-workflow-id%3A+documentation-updater%22&type=pullrequests)
> - [x] expires on Jun 24, 2026, 11:01 AM UTC