docs(linux): stop advertising a .deb package that isn't published (#990)

README's Quickstart badges linked a 'Download Debian .deb' button
straight to the releases page — but .deb bundling was deliberately
dropped from release.yml (tauri-cli bug, 'Failed to create control
scripts') and no release has ever shipped one. A community member
investigating #961 confirmed this by checking the actual release
assets. Users clicking that badge got a broken promise, not a package.

Removed the badge; docs/install/linux.md's '## Install (.deb)' section
now honestly states it's unavailable pending a tauri-cli fix, points to
the AppImage as the supported path, and keeps the historical pre-v0.3
.deb upgrade note (ffprobe conflict) since that's still relevant to
existing installs.

Co-authored-by: mergetest <test@local>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

docs/install/linux.md

@@ -5,7 +5,7 @@ working OmniVoice Studio install on a Debian / Ubuntu / Fedora / Arch host.
 
 ## Prerequisites
 
-### Using the AppImage or .deb
+### Using the AppImage
 
 - **Linux x86_64** with a desktop session (X11 or Wayland) capable of running
   a Tauri / WebKitGTK app.
@@ -73,12 +73,15 @@ No FUSE? Use `--appimage-extract-and-run`:
 ./OmniVoice.Studio_*.AppImage --appimage-extract-and-run
 ```
 
-## Install (.deb)
+## .deb package
 
-```bash
-sudo apt install ./OmniVoice.Studio_*.amd64.deb
-omnivoice-studio
-```
+Not currently published: `.deb` bundling is disabled in the release pipeline
+because of a `tauri-cli` bug (`Failed to create control scripts`) — see the
+comment in `.github/workflows/release.yml` for the tracking note. The
+AppImage above is the supported Linux install path until a `tauri-cli`
+version resolves it. `apt install`-able `.deb`s shipped before v0.3 (see
+[.deb ffprobe conflict](#deb-ffprobe-conflict) below) if you're upgrading
+from one of those.
 
 The desktop app uses these canonical paths (kept in sync with
 `scripts/desktop-prod.sh` by the docs-drift CI gate):