tui: remove the voice-input crate feature (#16467)

## Why

`voice-input` is the only remaining TUI crate feature, but it is also a
default feature and nothing in the workspace selects it explicitly. In
practice it is just acting as a proxy for platform support, which is
better expressed with target-specific dependencies and cfgs.

## What changed

- remove the `voice-input` feature from `codex-tui`
- make `cpal` a normal non-Linux target dependency
- replace the feature-based voice and audio cfgs with pure
Linux-vs-non-Linux cfgs
- shrink the workspace-manifest verifier allowlist to remove the
remaining `codex-tui` exception

## How tested

- `python3 .github/scripts/verify_cargo_workspace_manifests.py`
- `cargo test -p codex-tui`
- `just bazel-lock-check`
- `just argument-comment-lint -p codex-tui`

.github/scripts/verify_cargo_workspace_manifests.py

@@ -30,18 +30,8 @@ MANIFEST_FEATURE_EXCEPTIONS = {
     "codex-rs/otel/Cargo.toml": {
         "disable-default-metrics-exporter": (),
     },
-    "codex-rs/tui/Cargo.toml": {
-        "default": ("voice-input",),
-        "voice-input": ("dep:cpal",),
-    },
-}
-OPTIONAL_DEPENDENCY_EXCEPTIONS = {
-    (
-        "codex-rs/tui/Cargo.toml",
-        'target.cfg(not(target_os = "linux")).dependencies',
-        "cpal",
-    ),
 }
+OPTIONAL_DEPENDENCY_EXCEPTIONS = set()
 INTERNAL_DEPENDENCY_FEATURE_EXCEPTIONS = {
     (
         "codex-rs/core/Cargo.toml",

codex-rs/tui/Cargo.toml

@@ -17,10 +17,6 @@ path = "src/bin/md-events.rs"
 name = "codex_tui"
 path = "src/lib.rs"
 
-[features]
-default = ["voice-input"]
-voice-input = ["dep:cpal"]
-
 [lints]
 workspace = true
 
@@ -112,7 +108,7 @@ codex-windows-sandbox = { workspace = true }
 tokio-util = { workspace = true, features = ["time"] }
 
 [target.'cfg(not(target_os = "linux"))'.dependencies]
-cpal = { version = "0.15", optional = true }
+cpal = "0.15"
 
 [target.'cfg(unix)'.dependencies]
 libc = { workspace = true }

codex-rs/tui/src/app_command.rs

@@ -121,10 +121,7 @@ impl AppCommand {
         Self(Op::RealtimeConversationStart(params))
     }
 
-    #[cfg_attr(
+    #[cfg_attr(target_os = "linux", allow(dead_code))]
-        any(target_os = "linux", not(feature = "voice-input")),
-        allow(dead_code)
-    )]
     pub(crate) fn realtime_conversation_audio(params: ConversationAudioParams) -> Self {
         Self(Op::RealtimeConversationAudio(params))
     }

codex-rs/tui/src/app_event.rs

@@ -313,10 +313,7 @@ pub(crate) enum AppEvent {
     },
 
     /// Persist the selected realtime microphone or speaker to top-level config.
-    #[cfg_attr(
+    #[cfg_attr(target_os = "linux", allow(dead_code))]
-        any(target_os = "linux", not(feature = "voice-input")),
-        allow(dead_code)
-    )]
     PersistRealtimeAudioDeviceSelection {
         kind: RealtimeAudioDeviceKind,
         name: Option<String>,

codex-rs/tui/src/app_event_sender.rs

@@ -63,10 +63,7 @@ impl AppEventSender {
         ));
     }
 
-    #[cfg_attr(
+    #[cfg_attr(target_os = "linux", allow(dead_code))]
-        any(target_os = "linux", not(feature = "voice-input")),
-        allow(dead_code)
-    )]
     pub(crate) fn realtime_conversation_audio(&self, params: ConversationAudioParams) {
         self.send(AppEvent::CodexOp(
             AppCommand::realtime_conversation_audio(params).into_core(),

codex-rs/tui/src/lib.rs

@@ -79,9 +79,10 @@ mod app_event;
 mod app_event_sender;
 mod app_server_session;
 mod ascii_animation;
-#[cfg(all(not(target_os = "linux"), feature = "voice-input"))]
+#[cfg(not(target_os = "linux"))]
 mod audio_device;
-#[cfg(all(not(target_os = "linux"), not(feature = "voice-input")))]
+#[cfg(target_os = "linux")]
+#[allow(dead_code)]
 mod audio_device {
     use crate::app_event::RealtimeAudioDeviceKind;
 
@@ -151,9 +152,10 @@ pub mod update_action;
 mod update_prompt;
 mod updates;
 mod version;
-#[cfg(all(not(target_os = "linux"), feature = "voice-input"))]
+#[cfg(not(target_os = "linux"))]
 mod voice;
-#[cfg(all(not(target_os = "linux"), not(feature = "voice-input")))]
+#[cfg(target_os = "linux")]
+#[allow(dead_code)]
 mod voice {
     use crate::app_event_sender::AppEventSender;
     use codex_core::config::Config;