perf: apply (micro) optimization on SerializedHyphenationPatterns (#689)

This PR applies a micro optimization on `SerializedHyphenationPatterns`,
which allow reading `rootOffset` directly without having to parse then
cache it.

It should not affect storage space since no new bytes are added.

This also gets rid of the linear cache search whenever
`liangBreakIndexes` is called. In theory, the performance should be
improved a bit, although it may be too small to be noticeable in
practice.

master branch:

```
english: 99.1023%
french: 100%
german: 97.7289%
russian: 97.2167%
spanish: 99.0236%
```

This PR:

```
english: 99.1023%
french: 100%
german: 97.7289%
russian: 97.2167%
spanish: 99.0236%
```

---

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? PARTIALLY - mostly IDE
tab-autocompletions

scripts/generate_hyphenation_trie.py

@@ -33,10 +33,28 @@ def _symbol_from_output(path: pathlib.Path) -> str:
 
 def write_header(path: pathlib.Path, blob: bytes, symbol: str) -> None:
     # Emit a constexpr header containing the raw bytes plus a SerializedHyphenationPatterns descriptor.
+    # The binary format has:
+    #   - 4 bytes: big-endian root address
+    #   - levels tape: from byte 4 to root_addr
+    #   - nodes data: from root_addr onwards
+    
+    if len(blob) < 4:
+        raise ValueError(f"Blob too small: {len(blob)} bytes")
+    
+    # Parse root address (big-endian uint32)
+    root_addr = (blob[0] << 24) | (blob[1] << 16) | (blob[2] << 8) | blob[3]
+    
+    if root_addr > len(blob):
+        raise ValueError(f"Root address {root_addr} exceeds blob size {len(blob)}")
+    
+    # Remove the 4-byte root address and adjust the offset
+    bytes_literal = _format_bytes(blob[4:])
+    root_addr_new = root_addr - 4
+
     path.parent.mkdir(parents=True, exist_ok=True)
     data_symbol = f"{symbol}_trie_data"
     patterns_symbol = f"{symbol}_patterns"
-    bytes_literal = _format_bytes(blob)
+
     content = f"""#pragma once
 
 #include <cstddef>
@@ -50,6 +68,7 @@ alignas(4) constexpr uint8_t {data_symbol}[] = {{
 }};
 
 constexpr SerializedHyphenationPatterns {patterns_symbol} = {{
+    {f"0x{root_addr_new:02X}"}u,
     {data_symbol},
     sizeof({data_symbol}),
 }};