fix clicks from the menu bar app: find tmux without homebrew on PATH

launchd starts the menu bar app with PATH=/usr/bin:/bin:/usr/sbin:/sbin,
so the `dingger focus` it runs for every click (panel rows, menu rows, the
jump shortcut) could not find homebrew's tmux and failed with a misleading
"no tmux client attached"; the app discarded the error. dingger now finds
tmux on PATH or in the usual install locations (DINGGER_TMUX overrides),
reports a missing tmux as such, and the app logs failed jumps.

also: panel rows own every click inside them (labels took the clicks and
counted as window-drag background).

e2e step 14 repeats the menu bar row click and dingger focus under
launchd's environment; both fail with the previous binaries.

2 files changed, 29 insertions, 9 deletions

diff --git a/crates/dinggerd/src/main.rs b/crates/dinggerd/src/main.rs
index 285f83a..3707d51 100644
--- a/crates/dinggerd/src/main.rs
+++ b/crates/dinggerd/src/main.rs
@@ -125,7 +125,7 @@ fn main() {
 /// by the watcher on its next tick). This is the single code path behind
 /// every click: the tmux status line and the menu bar rows.
 fn focus(client: Option<String>, pane: Option<String>) -> Result<(), String> {
-    let clients = tmux::clients();
+    let clients = tmux::clients()?;
     // The named client if it is attached; otherwise the most recently active
     // one (a click on the status line makes the clicking client the most
     // recent, so this is right even if the name did not expand).
diff --git a/crates/dinggerd/src/tmux.rs b/crates/dinggerd/src/tmux.rs
index 6189c4b..48d9544 100644
--- a/crates/dinggerd/src/tmux.rs
+++ b/crates/dinggerd/src/tmux.rs
@@ -37,8 +37,30 @@ impl Pane {
     }
 }
 
+/// The tmux binary. launchd starts dingger, and the menu bar app that runs
+/// `dingger focus`, with PATH=/usr/bin:/bin:/usr/sbin:/sbin, where Homebrew's
+/// tmux is not found: fall back to the usual install locations.
+fn tmux_binary() -> &'static std::path::Path {
+    static TMUX: std::sync::OnceLock<std::path::PathBuf> = std::sync::OnceLock::new();
+    TMUX.get_or_init(|| {
+        if let Some(path) = std::env::var_os("DINGGER_TMUX") {
+            return path.into();
+        }
+        let on_path: Vec<std::path::PathBuf> = std::env::var_os("PATH")
+            .map(|path| std::env::split_paths(&path).map(|dir| dir.join("tmux")).collect())
+            .unwrap_or_default();
+        let known = ["/opt/homebrew/bin/tmux", "/usr/local/bin/tmux", "/usr/bin/tmux"]
+            .map(std::path::PathBuf::from);
+        on_path
+            .into_iter()
+            .chain(known)
+            .find(|candidate| candidate.is_file())
+            .unwrap_or_else(|| "tmux".into())
+    })
+}
+
 fn run_tmux(args: &[&str]) -> Result<String, String> {
-    let mut command = Command::new("tmux");
+    let mut command = Command::new(tmux_binary());
     // -u forces UTF-8 mode: without it, tmux mangles format output in
     // non-UTF-8 locales (launchd/cron default to the C locale, turning the
     // tab separators in our -F formats into underscores).
@@ -51,7 +73,7 @@ fn run_tmux(args: &[&str]) -> Result<String, String> {
     let output = command
         .args(args)
         .output()
-        .map_err(|err| format!("failed to run tmux: {err}"))?;
+        .map_err(|err| format!("failed to run tmux ({}): {err}", tmux_binary().display()))?;
     if !output.status.success() {
         let stderr = String::from_utf8_lossy(&output.stderr);
         return Err(format!("tmux {} failed: {}", args.join(" "), stderr.trim()));
@@ -227,14 +249,12 @@ pub fn client_format(client: &str, format: &str) -> Option<String> {
 }
 
 /// Attached clients as (name, pid), most recently active first.
-pub fn clients() -> Vec<(String, u32)> {
-    let Ok(out) = run_tmux(&[
+pub fn clients() -> Result<Vec<(String, u32)>, String> {
+    let out = run_tmux(&[
         "list-clients",
         "-F",
         "#{client_activity}\t#{client_name}\t#{client_pid}",
-    ]) else {
-        return Vec::new();
-    };
+    ])?;
     let mut clients: Vec<(u64, String, u32)> = out
         .lines()
         .filter_map(|line| {
@@ -246,7 +266,7 @@ pub fn clients() -> Vec<(String, u32)> {
         })
         .collect();
     clients.sort_by_key(|client| std::cmp::Reverse(client.0));
-    clients.into_iter().map(|(_, name, pid)| (name, pid)).collect()
+    Ok(clients.into_iter().map(|(_, name, pid)| (name, pid)).collect())
 }
 
 /// Show a pane in a client: switch the client to the pane's window and make