feat(php-shim): render human-facing timestamps in the local timezone

Split date() into date_utc() and date_local(), the latter resolving the
system's local timezone through the tzfile crate ($TZ, then
/etc/localtime, falling back to UTC when neither is readable). The
timestamps Composer renders for humans -- the GitHub OAuth token note,
the GitHub API rate limit reset time, the Perforce client spec fields and
the "today" check of the show command -- now go through date_local().

PHP resolves its default timezone from the date.timezone ini setting,
which Shirabe does not read, so date_default_timezone_get/set have no
input left to model and are dropped from the shim and its callers. The
resulting difference is recorded in docs/known-incompatibilities.md.

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

2 files changed, 6 insertions, 6 deletions

diff --git a/crates/shirabe/src/util/github.rs b/crates/shirabe/src/util/github.rs
index 26756ed0..25a95e57 100644
--- a/crates/shirabe/src/util/github.rs
+++ b/crates/shirabe/src/util/github.rs
@@ -10,7 +10,7 @@ use crate::util::ProcessExecutor;
 use indexmap::IndexMap;
 use shirabe_pcre::{CaptureKey, Preg};
 use shirabe_php_shim::Catch as _;
-use shirabe_php_shim::{PhpMixed, date, in_array_loose, php_regex, stripos, strtolower};
+use shirabe_php_shim::{PhpMixed, date_local, in_array_loose, php_regex, stripos, strtolower};
 
 #[derive(Debug)]
 pub struct GitHub {
@@ -106,7 +106,7 @@ impl GitHub {
                 note += &format!(" on {}", output.trim());
             }
         }
-        note += &format!(" {}", date("Y-m-d Hi", None));
+        note += &format!(" {}", date_local("Y-m-d Hi", None));
 
         let (local_name, auth_name): (Option<String>, String) = {
             let cfg = self.config.borrow();
@@ -309,7 +309,7 @@ impl GitHub {
                     let ts: i64 = value.trim().parse().unwrap_or(0);
                     rate_limit.insert(
                         "reset".to_string(),
-                        PhpMixed::String(date("Y-m-d H:i:s", Some(ts))),
+                        PhpMixed::String(date_local("Y-m-d H:i:s", Some(ts))),
                     );
                 }
                 _ => {}
diff --git a/crates/shirabe/src/util/perforce.rs b/crates/shirabe/src/util/perforce.rs
index 1820936c..246e37f5 100644
--- a/crates/shirabe/src/util/perforce.rs
+++ b/crates/shirabe/src/util/perforce.rs
@@ -8,7 +8,7 @@ use crate::util::ProcessExecutor;
 use indexmap::IndexMap;
 use shirabe_pcre::Preg;
 use shirabe_php_shim::{
-    Exception, PHP_EOL, PhpMixed, PhpResource, chdir, date, explode, fclose, feof, fgets,
+    Exception, PHP_EOL, PhpMixed, PhpResource, chdir, date_local, explode, fclose, feof, fgets,
     file_get_contents, fopen, fwrite, gethostname, json_decode, php_regex, str_replace_array,
     strcmp, strlen, strpos, strrpos, substr, time, trim,
 };
@@ -414,7 +414,7 @@ impl Perforce {
             spec,
             format!(
                 "Update: {}{}{}",
-                date("Y/m/d H:i:s", None),
+                date_local("Y/m/d H:i:s", None),
                 PHP_EOL,
                 PHP_EOL
             ),
@@ -422,7 +422,7 @@ impl Perforce {
         );
         fwrite(
             spec,
-            format!("Access: {}{}", date("Y/m/d H:i:s", None), PHP_EOL),
+            format!("Access: {}{}", date_local("Y/m/d H:i:s", None), PHP_EOL),
             None,
         );
         fwrite(