Record the Xcode version in .xcode-version

[aarmanroy]

Records the Xcode version CI already builds with (26.6) in a file contributors can actually find, since right now it only exists inside .github/workflows/ci.yml.

🤖 Generated with Claude Code

[pullfrog]

✅ No new issues found.

Reviewed changes

• Add .xcode-version with 26.6 — captures the Xcode version CI already uses (from ci.yml:49 and release.yml:27) in a convention file contributors can discover.

  ^{｜ View workflow run ｜ Using DeepSeek Pro ｜ 𝕏}

[sambitcreate]

Review findings

The .xcode-version value is valid and correctly matches the Xcode 26.6 toolchain used by CI, but I do not think this should merge as-is.

1. Blocking: this metadata-only change will trigger a production Aiden release. .github/workflows/release.yml runs on every push to main except Markdown, docs/**, and the release workflow itself. .xcode-version is not ignored, releases are enabled, and the workflow assigns a new version, signs/notarizes the app, and publishes the assets as the latest release. Please add .xcode-version to paths-ignore unless shipping a public app update for this metadata change is intentional.

2. The real CI suite has not run. The exact-head CI run is action_required with zero jobs because this PR comes from an external fork. Only Pullfrog passed. Please approve and run CI on commit 130bc88 before merge: https://github.com/sambitcreate/aiden-agent/actions/runs/30884048632

Minor documentation point: the PR description says Xcode 26.6 currently exists only in ci.yml, but it is also pinned in release.yml.