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>

3 files changed, 3 insertions, 20 deletions

diff --git a/crates/shirabe-php-shim/src/output.rs b/crates/shirabe-php-shim/src/output.rs
index 698f3bf4..d4d83200 100644
--- a/crates/shirabe-php-shim/src/output.rs
+++ b/crates/shirabe-php-shim/src/output.rs
@@ -1,6 +1,5 @@
 // PHP output buffering captures everything the interpreter would echo to stdout. The shim has no
-// general echo-to-buffer routing, and its only producer in Composer (`phpinfo`) depends on PHP
-// runtime configuration that is itself unmodeled, so a buffer here would silently capture nothing.
+// general echo-to-buffer routing, so a buffer here would silently capture nothing.
 pub fn ob_start() -> bool {
     todo!()
 }
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 {
diff --git a/crates/shirabe-php-shim/src/runtime.rs b/crates/shirabe-php-shim/src/runtime.rs
index 86cbfd74..2b5e7155 100644
--- a/crates/shirabe-php-shim/src/runtime.rs
+++ b/crates/shirabe-php-shim/src/runtime.rs
@@ -27,7 +27,6 @@ pub const E_USER_NOTICE: i64 = 1024;
 pub const E_DEPRECATED: i64 = 8192;
 pub const E_USER_DEPRECATED: i64 = 16384;
 
-pub const INFO_GENERAL: i64 = 1;
 pub const PHP_BINARY: &str = "";
 
 // NOTE: &str matching in const expression does not compile for now.
@@ -366,12 +365,6 @@ pub fn ini_set(_varname: &str, _value: &str) -> Option<String> {
     todo!()
 }
 
-pub fn phpinfo(_what: i64) {
-    // TODO(php-runtime): phpinfo() dumps the full PHP runtime configuration, which the shim does not
-    // model.
-    todo!()
-}
-
 pub fn sapi_windows_vt100_support(_resource: &crate::PhpResource) -> bool {
     // TODO(phase-c): Windows-only SAPI function; not defined on the non-Windows target this build
     // models (function_exists reports it absent).