feat(external-packages,shim): implement impl todos across components

Port seld/jsonlint JsonParser (+hand-written Lexer), unblocking 10 json_file
parse-error tests verified byte-for-byte against PHP. Implement Symfony Finder
SplFileInfo, executable finders, String classes (byte/code-point/unicode),
ZipArchive shim (via the zip crate), SPDX license validation, and shim
date/stream functions. Genuinely-blocked sites (reflection, PHP runtime
constants, non-UTF-8 transcoding, recursive PCRE) stay todo!() with reasons.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/crates/shirabe-external-packages/src/symfony/string/unicode_string.rs b/crates/shirabe-external-packages/src/symfony/string/unicode_string.rs
index 8917f20..e415846 100644
--- a/crates/shirabe-external-packages/src/symfony/string/unicode_string.rs
+++ b/crates/shirabe-external-packages/src/symfony/string/unicode_string.rs
@@ -34,11 +34,23 @@ impl UnicodeString {
         width
     }
 
+    // TODO(phase-d): the faithful `length()` uses `grapheme_strlen` (extended grapheme clusters),
+    // which needs Unicode segmentation tables with no Rust std equivalent and no permitted crate.
+    // Approximated with the code-point count, exact only when no combining/multi-code-point
+    // clusters are present (e.g. ASCII).
     pub fn length(&self) -> i64 {
-        todo!()
+        shirabe_php_shim::mb_strlen(&self.string, "UTF-8")
     }
 
-    pub fn slice(&self, _start: i64, _length: Option<i64>) -> Self {
-        todo!()
+    // TODO(phase-d): the faithful `slice()` uses `grapheme_substr` (grapheme-cluster offsets), which
+    // needs Unicode segmentation tables with no std equivalent and no permitted crate. Approximated
+    // with code-point offsets via `mb_substr`, exact only without combining/multi-code-point clusters.
+    pub fn slice(&self, start: i64, length: Option<i64>) -> Self {
+        Self::new(&shirabe_php_shim::mb_substr(
+            &self.string,
+            start,
+            length,
+            Some("UTF-8"),
+        ))
     }
 }