refactor(preg): split PregMatches reads into get() and name()

PregMatches keyed both forms of a capture group through CaptureKey, so
every read built one: a usize wrapped in an enum, or worse, a String
allocated to name a group that regex::Captures can look up from a &str.
It now mirrors regex::Captures instead -- get() takes the group number,
name() the group name -- and the enum drops out of the type entirely.

That is 285 call sites across 59 files, and the named ones carry most of
the win: `matches.get(&CaptureKey::ByName("host".to_string()))` reads as
`matches.name("host")`. ProcessExecutor loses a `user_key` binding that
existed only to build the key once.

CaptureKey stays as the key type of PregMatchesAll and
PregMatchesAllWithOffsets, where numbered and named entries share one
IndexMap and a key type is the point. Five files still name it.

Also retargets the two preg_match_all comments that described the
occurrence count through `matches[&CaptureKey::ByIndex(0)].len()`, an
Index impl these types no longer carry.

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

1 files changed, 3 insertions, 6 deletions

diff --git a/crates/shirabe/src/util/platform.rs b/crates/shirabe/src/util/platform.rs
index f2b8aea3..606ff43d 100644
--- a/crates/shirabe/src/util/platform.rs
+++ b/crates/shirabe/src/util/platform.rs
@@ -83,7 +83,6 @@ impl Platform {
 
     /// Parses tildes and environment variables in paths.
     pub fn expand_path(path: &str) -> String {
-        use shirabe_pcre::CaptureKey;
         if Preg::is_match(php_regex!(r"#^~[\\/]#"), path) {
             return format!(
                 "{}{}",
@@ -100,12 +99,10 @@ impl Platform {
             php_regex!(r"#^(?:\$(?P<dvar>\w+)|%(?P<pvar>\w+)%)(?P<path>.*)#"),
             |matches: &PregMatches| -> String {
                 let var = matches
-                    .get(&CaptureKey::ByName("dvar".to_string()))
-                    .or_else(|| matches.get(&CaptureKey::ByName("pvar".to_string())))
-                    .unwrap_or("");
-                let path_part = matches
-                    .get(&CaptureKey::ByName("path".to_string()))
+                    .name("dvar")
+                    .or_else(|| matches.name("pvar"))
                     .unwrap_or("");
+                let path_part = matches.name("path").unwrap_or("");
                 // Treat HOME as an alias for USERPROFILE on Windows for legacy reasons
                 if Platform::is_windows() && var == "HOME" {
                     let home =