terminal commands are silent when tmux runs them

tmux shows a hook's output and a non-zero exit in view mode over the pane.
the focus hook's normal outcomes (focus moved on, Ghostty not in front)
exited 1, and the one-second settling made "focus moved on" common:
"'dingger terminal focused --client ...' returned 1" kept covering panes.
`dingger terminal focused` and `terminal raise` now always exit 0 and
print nothing unless run by hand.

tmux::client_format checks that tmux answered for the client asked about:
for a client that is gone, tmux answers for the current one, so a raise
for a client that had just detached raised another client's terminal.

e2e step 20: no pane in view mode after the hook's failures, a gone
client raises nothing, and a focus held past the settling second; the old
code fails the new checks.

1 files changed, 14 insertions, 3 deletions

diff --git a/crates/dinggerd/src/main.rs b/crates/dinggerd/src/main.rs
index e43f9a7..b97471c 100644
--- a/crates/dinggerd/src/main.rs
+++ b/crates/dinggerd/src/main.rs
@@ -13,6 +13,7 @@ mod tmux;
 mod watcher;
 
 use clap::{Parser, Subcommand};
+use std::io::IsTerminal;
 use tracing_subscriber::EnvFilter;
 
 #[derive(Parser)]
@@ -128,7 +129,14 @@ fn main() {
     let cli = Cli::parse();
     // The daemon logs its work; commands print their own output and only
     // log problems.
-    let default_level = if matches!(cli.command, Command::Watch { .. }) { "info" } else { "warn" };
+    // tmux shows whatever its hooks print, and a non-zero exit, as a
+    // message: the commands tmux runs are silent unless run by hand.
+    let by_tmux = matches!(cli.command, Command::Terminal { .. }) && !std::io::stderr().is_terminal();
+    let default_level = match cli.command {
+        Command::Watch { .. } => "info",
+        _ if by_tmux => "off",
+        _ => "warn",
+    };
     tracing_subscriber::fmt()
         .with_env_filter(EnvFilter::try_from_default_env().unwrap_or_else(|_| default_level.into()))
         .init();
@@ -197,9 +205,12 @@ fn main() {
                 TerminalAction::Focused { client } => terminals::learn(client),
                 TerminalAction::Raise { client } => terminals::raise(client),
             };
+            // Best effort, run by tmux (the focus hook, a raise): an outcome
+            // like "focus moved on" or "terminal gone" is not a failure.
             if let Err(err) = result {
-                eprintln!("dingger: {err}");
-                std::process::exit(1);
+                if !by_tmux {
+                    eprintln!("dingger: {err}");
+                }
             }
         }
         // Never fails the agent: exits 0, prints nothing.