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

apps/desktop/element.io/healthchat/README

@@ -45,11 +45,13 @@ CI
 --
 .github/workflows/build-healthchat-desktop.yaml builds the plugin + webapp artifact and
 feeds it into build_desktop_prepare.yaml (`config: element.io/healthchat`,
-`webapp-artifact: healthchat-webapp`) and the per-platform build_desktop_{linux,macos,windows}.yaml
+`webapp-artifact: healthchat-webapp`) and the per-platform build_desktop_{macos,windows}.yaml
 reusables. It runs on every `healthchat-v*` tag (alongside the web build) and via
 workflow_dispatch. The reusables are pointed at THIS fork (`repository`/`ref` inputs) so the
 Electron shell, icons and the healthchat:// deep-link handler are fork-branded. On a tag push the
-`release` job attaches the .dmg / .zip / .exe / .msi / .deb / .tar.gz to the GitHub Release.
+`release` job attaches the .dmg / .zip / .exe / .msi to the GitHub Release.
+(Linux is not built: the upstream build_desktop_linux.yaml needs a build-env Docker image
+keyed by commit SHA that only exists in the upstream element-hq registry, so it can't run here.)
 
 Branding assets
 ---------------

apps/desktop/package.json

@@ -3,7 +3,7 @@
     "productName": "Element",
     "main": "lib/electron-main.js",
     "exports": "./lib/electron-main.js",
-    "version": "1.1.1",
+    "version": "1.1.2",
     "description": "Element: the future of secure communication",
     "author": {
         "name": "Element",