desktop: one name across all three install channels (issue 2075)

The app answered to three different names depending on how it arrived, and the
part that actually hurt was WM_CLASS. Reading tauri-bundler settles what it is:
the generated .desktop template writes StartupWMClass={{exec}} where exec is
main_binary_name, and tao creates its GtkApplication with a NULL app id
(enableGTKAppId defaults off), so GTK falls back to the program name. WM_CLASS
is the binary name, nothing else.

Which inverts this issue's premise. The rename could not break grouping,
because two channels weren't grouping in the first place: pacman ships
/usr/bin/thoughtsync and the AppImage's AppRun execs thoughtsync-desktop, while
all three hand-written entries hardcoded StartupWMClass=ThoughtSync — a string
no binary in any channel has ever reported. Only the .deb worked, and only
because Tauri generates its entry from the binary and never consulted us.

So: thoughtsync everywhere, carried by the build target itself via Cargo [[bin]]
plus mainBinaryName rather than by the install path, since the target name is
what the desktop reads. The pacman package sheds its -desktop suffix and
declares conflict+replaces so an upgrade retires the old one instead of landing
beside it and fighting over /usr/bin/thoughtsync.

The .deb verifier now asserts binary path, Exec and StartupWMClass all agree,
which is the part that keeps this fixed: the .deb's entry is the one no human
writes, so it's the one that drifts silently.

Package: thought-sync stays. tauri-bundler derives it as kebab-case(productName)
with no override, and rewriting a control archive on every build is a poor trade
for one uninstall command.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

desktop/src-tauri/Cargo.toml

@@ -4,6 +4,10 @@ version = "0.1.0"
 description = "ThoughtSync desktop — local-first Keep-style thought capture"
 authors = ["bvandeusen"]
 edition = "2021"
+# The executable is named below, not inferred from this package name. Off so the
+# inferred `thoughtsync-desktop` target and the explicit one can't both claim
+# src/main.rs.
+autobins = false
 
 # App logic lives in the library (Tauri v2 pattern: a single `run()` entry point
 # reusable across desktop and any future mobile target); main.rs is a thin shim.
@@ -11,6 +15,17 @@ edition = "2021"
 name = "thoughtsync_desktop_lib"
 crate-type = ["staticlib", "cdylib", "rlib"]
 
+# The shipped command is `thoughtsync` on every install channel, and the binary's
+# own name is what the desktop actually keys on: GTK derives the window's WM_CLASS
+# from it, and Tauri's generated .desktop file writes `StartupWMClass={binary}`.
+# So the canonical name has to be carried by the build target itself, not just by
+# the path it gets installed to (issue 2075). The crate stays `thoughtsync-desktop`
+# — only the executable is renamed. `thoughtsync` is also fixed under kebab-casing,
+# which the AppImage bundler applies to the binary name on its way in.
+[[bin]]
+name = "thoughtsync"
+path = "src/main.rs"
+
 [build-dependencies]
 tauri-build = { version = "2", features = [] }