fix(dbus): stop forcing the zbus 5 executor onto tokio

zbus features unify across the dependency graph and "tokio" wins over
"async-io": enabling it via rfd, ashpd (secret portal) and ksni's
default features flipped the shared zbus 5 executor to tokio for
accesskit_unix/atspi too — Slint's accessibility backend opens its
D-Bus connection on a plain thread and panicked at startup ("there is
no reactor running, must be called from the context of a Tokio 1.x
runtime"), killing AT-SPI support. Switch every zbus-5 consumer we
control to the async-io backend (rfd "async-std", ashpd "async-io",
ksni default-features off + "async-io"): async-io connections
self-drive from any thread and the futures still await fine inside our
tokio runtime. The zbus 4 group (keyring/secret-service/mpris-server/
qbz-audio) is a separate feature graph and stays on tokio by design.

cc

crates/Cargo.lock

@@ -411,6 +411,8 @@ version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d2f3f79755c74fd155000314eb349864caa787c6592eace6c6882dad873d9c39"
 dependencies = [
+ "async-fs",
+ "async-net",
  "enumflags2",
  "futures-channel",
  "futures-util",
@@ -418,7 +420,6 @@ dependencies = [
  "raw-window-handle",
  "serde",
  "serde_repr",
- "tokio",
  "url",
  "wayland-backend",
  "wayland-client",
@@ -436,7 +437,6 @@ dependencies = [
  "futures-util",
  "getrandom 0.4.2",
  "serde",
- "tokio",
  "zbus 5.15.0",
 ]
 
@@ -518,6 +518,17 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "async-net"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b948000fad4873c1c9339d60f2623323a0cfd3816e5181033c6a5cb68b2accf7"
+dependencies = [
+ "async-io",
+ "blocking",
+ "futures-lite",
+]
+
 [[package]]
 name = "async-process"
 version = "2.5.0"
@@ -3683,11 +3694,15 @@ version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a7ca513d0be42df5edb485af9f44a12b2cb85af773d91c27dc796d1c58b78edc"
 dependencies = [
+ "async-executor",
+ "async-io",
+ "async-lock",
+ "futures-channel",
+ "futures-lite",
  "futures-util",
  "once_cell",
  "pastey 0.2.3",
  "serde",
- "tokio",
  "zbus 5.15.0",
 ]
 
@@ -9898,7 +9913,6 @@ dependencies = [
  "rustix 1.1.4",
  "serde",
  "serde_repr",
- "tokio",
  "tracing",
  "uds_windows",
  "uuid 1.22.0",

crates/qbz-credentials/Cargo.toml

@@ -19,4 +19,10 @@ dirs = "6"
 keyring = { version = "3", features = ["async-secret-service", "crypto-rust"] }
 
 [target.'cfg(target_os = "linux")'.dependencies]
-ashpd = { version = "0.13", default-features = false, features = ["tokio", "secret"] }
+# async-io, NOT tokio: zbus features unify across the whole dependency graph
+# and its "tokio" feature wins over "async-io" — enabling it here flipped the
+# zbus 5 executor to tokio for accesskit_unix/atspi/ksni too, whose D-Bus
+# connections live on plain threads => startup panic "there is no reactor
+# running" and dead AT-SPI accessibility. async-io futures are runtime-
+# agnostic, so our portal call still awaits fine inside tokio.
+ashpd = { version = "0.13", default-features = false, features = ["async-io", "secret"] }

crates/qbz-media-controls/Cargo.toml

@@ -30,10 +30,14 @@ urlencoding = "2"
 [target.'cfg(target_os = "linux")'.dependencies]
 mpris-server = "0.8"
 async-channel = "2"
-# XDG notification portal (goes over D-Bus). Same crate + tokio runtime the
-# secret portal already pulls in (qbz-credentials uses ashpd 0.13/tokio).
+# XDG notification portal (goes over D-Bus). async-io, NOT tokio: zbus 5's
+# "tokio" feature unifies graph-wide and its executor then requires a tokio
+# reactor on EVERY thread that opens a zbus connection — accesskit_unix/atspi
+# (Slint accessibility) and ksni run theirs on plain threads and panicked at
+# startup ("there is no reactor running"). async-io futures still await fine
+# inside our tokio runtime. Keep in sync with qbz-credentials/Cargo.toml.
 ashpd = { version = "0.13", default-features = false, features = [
-    "tokio",
+    "async-io",
     "notification",
 ] }
 

crates/qbz/Cargo.toml

@@ -59,7 +59,10 @@ image = { version = "0.25", default-features = false, features = ["jpeg", "png"]
 urlencoding = "2"
 open = "5"
 arboard = "3"
-rfd = { version = "0.15", default-features = false, features = ["xdg-portal", "tokio"] }
+# async-std (rfd's name for the async-io/ashpd backend), NOT tokio: zbus 5's
+# "tokio" feature unifies graph-wide and breaks accesskit/atspi/ksni threads
+# (see the ashpd comment in qbz-credentials/Cargo.toml).
+rfd = { version = "0.15", default-features = false, features = ["xdg-portal", "async-std"] }
 serde = { workspace = true }
 serde_json = { workspace = true }
 dirs = "5"
@@ -126,7 +129,11 @@ i-slint-renderer-femtovg = { version = "=1.16.1", features = ["wgpu"] }
 # Activate / SecondaryActivate / Scroll. macOS/Windows use `tray-icon` instead
 # (added with the CustomApplicationHandler slice).
 [target.'cfg(target_os = "linux")'.dependencies]
-ksni = { version = "0.3", features = ["blocking"] }
+# default-features = false: ksni's default is "tokio", which flips the shared
+# zbus 5 executor to tokio graph-wide (breaks accesskit/atspi plain-thread
+# connections — see the rfd comment above). We only use the blocking API on
+# worker threads; async-io self-drives the connection from any context.
+ksni = { version = "0.3", default-features = false, features = ["blocking", "async-io"] }
 
 # macOS menu-bar tray (NSStatusItem), hand-rolled directly on objc2 0.5 /
 # app-kit 0.2 — the SAME objc2 generation winit 0.30 uses — so the NSMenu lives