refactor(symfony-process): drop the --enable-sigchild workarounds

isSigchildEnabled() detects a PHP built with --enable-sigchild, where PHP
reaps children itself and proc_get_status()/proc_terminate() stop reporting
or reaching them. Shirabe spawns child processes from Rust, so that build
option cannot affect them and every sigchild branch was unreachable.

Removing the branches retires the state that existed only to feed them:
fallbackStatus (written by the fourth pipe and by doSignal, read only by
the sigchild merge in updateStatus) and useFileHandles (whose sole reader
was the sigchild condition). shirabe-php-shim loses phpinfo(),
INFO_GENERAL and posix_kill(), which had no other callers.

DiagnoseCommand keeps its --enable-sigchild warning: it reports on the
user's PHP installation, not on how Shirabe runs processes.

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

1 files changed, 2 insertions, 11 deletions

diff --git a/crates/shirabe-php-shim/src/process.rs b/crates/shirabe-php-shim/src/process.rs
index 2b380c60..b082f472 100644
--- a/crates/shirabe-php-shim/src/process.rs
+++ b/crates/shirabe-php-shim/src/process.rs
@@ -380,12 +380,7 @@ pub fn proc_terminate(process: &PhpResource, signal: i64) -> bool {
     let Some(child) = state.child.as_ref() else {
         return false;
     };
-    send_signal(child.id() as i32, signal)
-}
-
-/// Shared body of `proc_terminate` and `posix_kill`. Signal 0 is PHP's existence probe and is
-/// forwarded to `kill(2)` as such.
-fn send_signal(pid: i32, signal: i64) -> bool {
+    // Signal 0 is PHP's existence probe and is forwarded to `kill(2)` as such.
     let signal = if signal == 0 {
         None
     } else {
@@ -394,7 +389,7 @@ fn send_signal(pid: i32, signal: i64) -> bool {
             Err(_) => return false,
         }
     };
-    nix::sys::signal::kill(nix::unistd::Pid::from_raw(pid), signal).is_ok()
+    nix::sys::signal::kill(nix::unistd::Pid::from_raw(child.id() as i32), signal).is_ok()
 }
 
 pub fn getmypid() -> i64 {
@@ -466,10 +461,6 @@ pub fn posix_isatty(stream: PhpResource) -> bool {
     }
 }
 
-pub fn posix_kill(pid: i64, signal: i64) -> bool {
-    send_signal(pid as i32, signal)
-}
-
 /// PHP `get_current_user()`: the name of the owner of the running script file. The Shirabe
 /// executable takes the place of the script; PHP returns an empty string when the lookup fails.
 pub fn get_current_user() -> String {