docs: roadmap item for GitHub release update check

Plan a best-effort, opt-in check that compares app.Version against the
latest published GitHub Release and surfaces an "Update available" hint in
Settings — detection and notification only, no auto-download.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/ROADMAP.md

@@ -5,6 +5,37 @@ Completed work is recorded in [CHANGELOG.md](CHANGELOG.md), not here.
 
 ## Open Items
 
+### Update check from GitHub releases
+
+Releases are published as GitHub Releases (tags like `v0.12.0`, built by
+`.github/workflows/release.yml`), but the app never tells the user a newer
+version exists — they have to check the releases page by hand.
+
+Add an update check that queries the GitHub Releases API
+(`GET /repos/<owner>/<repo>/releases/latest`) for the latest published tag,
+strips the leading `v`, and compares it against `app.Version`. When a newer
+version is available, surface it non-intrusively — an "Update available"
+line in Settings (next to the existing version/build info) with a hyperlink
+to the release page, not a modal on launch.
+
+Design notes / open questions:
+
+- *Opt-in and offline-safe.* The check makes a network request, so it must be
+  off by default (or clearly consented) and never block startup. Failures
+  (offline, rate-limited, API change) should be silent — no error dialogs for a
+  best-effort convenience feature.
+- *Version comparison.* Compare semantic versions, not strings, so `0.12.0`
+  reads as newer than `0.9.0`. A tiny semver comparator in `app` (or a small
+  dependency) avoids lexical bugs.
+- *Where the check lives.* Keep it in the `app` layer behind the Service so the
+  UI only renders the result, and cache the last check so opening Settings
+  repeatedly does not spam the API (unauthenticated GitHub allows 60 req/h).
+- *Repo coordinates.* The primary remote is Gitea; the GitHub owner/repo used
+  for releases must be wired in explicitly (constant or build-time value) rather
+  than derived from `origin`.
+- *No auto-download.* Scope is detection and notification only; installing the
+  update stays a manual click-through to the release page.
+
 ### Window size persistence *(frozen)*
 
 Window size is currently **not** saved on quit or close. Saving was disabled