refactor(seld-signal): extract seld/signal into the shirabe-seld-signal crate

Move `Seld\Signal` out of shirabe-external-packages and into its own
crate, so the path is `shirabe_seld_signal::SignalHandler` instead of
`shirabe_external_packages::seld::signal::SignalHandler`.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

2 files changed, 28 insertions, 0 deletions

diff --git a/crates/shirabe-seld-signal/src/lib.rs b/crates/shirabe-seld-signal/src/lib.rs
new file mode 100644
index 00000000..16f51510
--- /dev/null
+++ b/crates/shirabe-seld-signal/src/lib.rs
@@ -0,0 +1,3 @@
+pub mod signal_handler;
+
+pub use signal_handler::*;
diff --git a/crates/shirabe-seld-signal/src/signal_handler.rs b/crates/shirabe-seld-signal/src/signal_handler.rs
new file mode 100644
index 00000000..b2f1873e
--- /dev/null
+++ b/crates/shirabe-seld-signal/src/signal_handler.rs
@@ -0,0 +1,25 @@
+//! ref: composer/vendor/seld/signal-handler/src/SignalHandler.php
+
+#[derive(Debug)]
+pub struct SignalHandler;
+
+// TODO(phase-c): disable signal handler at all for now.
+impl SignalHandler {
+    pub const SIGINT: &'static str = "SIGINT";
+    pub const SIGTERM: &'static str = "SIGTERM";
+    pub const SIGHUP: &'static str = "SIGHUP";
+
+    pub fn create(_signals: Vec<String>, _callback: Box<dyn Fn(String, &SignalHandler)>) -> Self {
+        Self
+    }
+
+    pub fn unregister(&self) {}
+
+    pub fn exit_with_last_signal(&self) {
+        std::process::exit(0);
+    }
+
+    pub fn is_triggered(&self) -> bool {
+        false
+    }
+}