refactor(app): clarify application and binary roles

Rename the application Cargo package from irtt-cli to irtt-rs
(crates/irtt-cli -> crates/irtt-app), and hard-rename its scriptable
client binary from irtt-cli to irtt-client, now that the application
also ships a first-class server and the old name reads as an umbrella
CLI for both roles.

Give each dedicated binary (irtt-client, irtt-tui, irtt-server) its
own entry point instead of funneling through the multicall
dispatcher's argv0/subcommand logic, so a dedicated binary only links
the applet code for the role it implements and always runs that role
regardless of the name it's invoked or copied under. irtt-rs remains
the feature-selectable multicall dispatcher and is now the only binary
that inspects argv0 or subcommands.

Move future application releases to the irtt-rs/vX.Y.Z tag namespace
(regenerated via `dist generate`), and bump the application package to
0.6.0 as a breaking distribution change. Library crate versions are
unaffected.

crates/irtt-app/src/shared/client/session.rs

@@ -0,0 +1,141 @@
+use std::sync::atomic::{AtomicBool, Ordering};
+
+#[cfg(any(feature = "client", feature = "tui"))]
+use irtt_client::managed::{ManagedEvent, ManagedEventSubscription, ManagedEventTryRecvError};
+
+#[cfg(any(feature = "client", feature = "tui"))]
+pub(crate) const MANAGED_EVENT_WORK_BUDGET: usize = 128;
+
+#[cfg(any(feature = "client", feature = "tui"))]
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(crate) enum ManagedDrainState {
+    Empty,
+    Closed,
+    BudgetExhausted,
+}
+
+/// Drain a bounded amount of lossy presentation work before returning to the
+/// frontend control loop.
+#[cfg(any(feature = "client", feature = "tui"))]
+pub(crate) fn drain_managed_events<E>(
+    events: &mut ManagedEventSubscription,
+    dropped_events: &mut u64,
+    mut process: impl FnMut(ManagedEvent) -> Result<(), E>,
+) -> Result<ManagedDrainState, E> {
+    for _ in 0..MANAGED_EVENT_WORK_BUDGET {
+        match events.try_recv() {
+            Ok(event) => process(event)?,
+            Err(ManagedEventTryRecvError::Lagged(count)) => {
+                *dropped_events = dropped_events.saturating_add(count);
+            }
+            Err(ManagedEventTryRecvError::Empty) => return Ok(ManagedDrainState::Empty),
+            Err(ManagedEventTryRecvError::Closed) => return Ok(ManagedDrainState::Closed),
+        }
+    }
+    Ok(ManagedDrainState::BudgetExhausted)
+}
+
+pub fn is_shutdown_requested(shutdown_requested: &AtomicBool) -> bool {
+    shutdown_requested.load(Ordering::Relaxed)
+}
+
+pub fn should_print_final_summary(continuous: bool, interrupted: bool) -> bool {
+    !continuous || interrupted
+}
+
+pub fn peer_close_run_error(
+    continuous: bool,
+    interrupted: bool,
+    peer_closed_target_outcomes: u64,
+) -> Option<String> {
+    if !continuous || interrupted || peer_closed_target_outcomes == 0 {
+        return None;
+    }
+
+    let sessions = if peer_closed_target_outcomes == 1 {
+        "target session"
+    } else {
+        "target sessions"
+    };
+    Some(format!(
+        "continuous run ended because of peer closure ({peer_closed_target_outcomes} {sessions})"
+    ))
+}
+
+pub fn request_managed_stop_for_peer_close(
+    continuous: bool,
+    interrupted: bool,
+    peer_closed_target_outcomes: u64,
+    stop_requested: &mut bool,
+) -> bool {
+    if !continuous || interrupted || peer_closed_target_outcomes == 0 {
+        return false;
+    }
+    request_managed_stop_once(stop_requested)
+}
+
+pub fn request_managed_stop_once(stop_requested: &mut bool) -> bool {
+    if *stop_requested {
+        return false;
+    }
+    *stop_requested = true;
+    true
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn peer_close_run_error_is_run_mode_and_interruption_aware() {
+        assert_eq!(peer_close_run_error(false, false, 1), None);
+        assert_eq!(peer_close_run_error(true, false, 0), None);
+        assert_eq!(peer_close_run_error(true, true, 1), None);
+        assert_eq!(
+            peer_close_run_error(true, false, 1).as_deref(),
+            Some("continuous run ended because of peer closure (1 target session)")
+        );
+        assert_eq!(
+            peer_close_run_error(true, false, 3).as_deref(),
+            Some("continuous run ended because of peer closure (3 target sessions)")
+        );
+    }
+
+    #[test]
+    fn grouped_peer_close_stop_policy_is_run_mode_and_one_shot() {
+        let mut stop_requested = false;
+        assert!(!request_managed_stop_for_peer_close(
+            false,
+            false,
+            1,
+            &mut stop_requested,
+        ));
+        assert!(!request_managed_stop_for_peer_close(
+            true,
+            true,
+            1,
+            &mut stop_requested,
+        ));
+        assert!(!request_managed_stop_for_peer_close(
+            true,
+            false,
+            0,
+            &mut stop_requested,
+        ));
+        assert!(!stop_requested);
+
+        assert!(request_managed_stop_for_peer_close(
+            true,
+            false,
+            1,
+            &mut stop_requested,
+        ));
+        assert!(stop_requested);
+        assert!(!request_managed_stop_for_peer_close(
+            true,
+            false,
+            1,
+            &mut stop_requested,
+        ));
+    }
+}