chore(release): HealthChat 1.1.2

Remove the Linux desktop build from the release pipeline. It could never
succeed in this fork: the upstream Linux reusable pulls a build-env Docker
image keyed by the building commit's SHA from the upstream element-hq
registry, where the fork's SHA does not exist, so every tagged build failed
with `manifest unknown`. Desktop releases now ship macOS and Windows only.

- Drop the linux job + its release artifacts from build-healthchat-desktop.yaml
- Bump apps/desktop/package.json to 1.1.2
- Update releasing-healthchat skill + desktop README docs

.claude/skills/releasing-healthchat/SKILL.md

@@ -13,17 +13,19 @@ Releases are driven by git tags of the form `healthchat-v<semver>` pushed to
   `:<sha>`, and creates a GitHub Release whose body is the matching section of
   `HEALTHCHAT_CHANGES.md`.
 - `.github/workflows/build-healthchat-desktop.yaml` (desktop) — builds the Electron
-  app for Linux (amd64/arm64), macOS (universal, signed+notarised) and Windows
-  (x64/arm64, signed), and attaches the installers (.dmg/.zip/.exe/.msi/.deb/.tar.gz)
-  to the **same** GitHub Release. The two workflows create-if-missing then upload, so
-  they race safely.
+  app for macOS (universal, signed+notarised) and Windows (x64/arm64, signed), and
+  attaches the installers (.dmg/.zip/.exe/.msi) to the **same** GitHub Release. The two
+  workflows create-if-missing then upload, so they race safely. (Linux is intentionally
+  not built — the upstream Linux reusable pulls a build-env Docker image keyed by commit
+  SHA that only exists in the upstream element-hq registry, so it cannot succeed in this
+  fork.)
 
 Publish target: **ghcr.io Docker image + GitHub Release (web bundle + desktop
 installers).** No npm, no mobile fan-out.
 
 The desktop app version is taken from `apps/desktop/package.json` (the per-job
 `version` input cannot set it — Windows squirrel mangles it into a nightly string,
-and on macOS/Linux it only feeds the update manifest). So `apps/desktop/package.json`
+and on macOS it only feeds the update manifest). So `apps/desktop/package.json`
 **must be bumped to the release version in the release commit** to keep the About
 dialog and installer filenames matching the tag. This is no longer optional: the
 desktop workflow's "Assert desktop app version matches release" step fails the build
@@ -162,7 +164,7 @@ warning. Prefer fixing the changelog over relying on the fallback.
       (`docker buildx imagetools inspect ghcr.io/<owner>/healthchat-web:stable`).
 - [ ] The desktop workflow run ("Build HealthChat Desktop") is green and the
       GitHub Release has the desktop installers attached (.dmg, *-mac.zip, *.msi,
-      "* Setup*.exe", *.deb, *.tar.gz).
+      "* Setup*.exe").
 - [ ] Smoke-check signing: macOS `spctl -a -vvv -t install <app>` is accepted;
       Windows installer shows a valid publisher (no SmartScreen block).
 
@@ -219,6 +221,7 @@ conflict on rebase, re-apply the HealthChat changes rather than blindly taking
 either side:
 
 - `.github/workflows/build_desktop_prepare.yaml`
-- `.github/workflows/build_desktop_linux.yaml`
+- `.github/workflows/build_desktop_linux.yaml` (still in the tree, but no longer
+  invoked by `build-healthchat-desktop.yaml` — the fork doesn't build Linux)
 - `.github/workflows/build_desktop_macos.yaml`
 - `.github/workflows/build_desktop_windows.yaml`