refactor(preg): report unmatched groups as null in the vec-shaped preg_*

preg_match_all() and preg_match_all_set_order() were the last preg_*
functions handing back a bare Vec<String>, where a group that did not
participate is indistinguishable from one that captured "". Hand back
Option<String> as the map-shaped functions already do; php_match_row(),
the last of the truncate-then-pad helpers, goes with them.

preg_split_delim_capture() keeps its Vec<String>. preg_split() accepts
no PREG_UNMATCHED_AS_NULL, so there is no null form to move it to, and
its result interleaves split segments -- which can never be absent --
with the captured delimiters.

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

1 files changed, 11 insertions, 1 deletions

diff --git a/crates/shirabe-symfony-console/src/completion/completion_input.rs b/crates/shirabe-symfony-console/src/completion/completion_input.rs
index 2f146a39..aafa7c8a 100644
--- a/crates/shirabe-symfony-console/src/completion/completion_input.rs
+++ b/crates/shirabe-symfony-console/src/completion/completion_input.rs
@@ -34,7 +34,17 @@ impl CompletionInput {
             input_str,
         );
 
-        Self::from_tokens(tokens[0].clone(), current_index)
+        Self::from_tokens(
+            tokens[0]
+                .iter()
+                .map(|token| {
+                    token
+                        .clone()
+                        .expect("group 0 participates whenever the pattern matches")
+                })
+                .collect(),
+            current_index,
+        )
     }
 
     /// Create an input based on an COMP_WORDS token list.