style(scan): Rust 스캐너 정규표현식을 모듈 상수로 hoist (성능 효과 없음 -- 측정은 PR 코멘트 참조)

.jules/bolt.md

@@ -54,3 +54,4 @@
 ## 2026-09-01 - 대용량 문자열 서브스트링 스캐닝 루프 최적화
 **Learning:** 긴 텍스트에서 여러 기준 문자열(`candidate`)을 탐색하여 다음 구역의 시작점을 찾을 때, 텍스트 전체에 대해 반복적으로 `text.find(candidate)`를 호출하면 O(N)의 비효율적인 중복 스캐닝 오버헤드가 발생합니다. 특히 가장 가까운 시작점을 찾기 위해 모든 후보를 스캔할 때 이 문제가 심화됩니다.
 **Action:** 기준점(`start`)을 잡은 후, `idx = text.find(candidate, start, end)`를 사용하여 검색 범위를 동적으로 축소(`end = min(end, idx)`)하십시오. 이렇게 하면 불필요한 스캐닝 오버헤드를 막고 검색 범위를 안전하게 줄여 매우 큰 성능 향상을 얻을 수 있습니다.
+## 2026-09-05 - Python re.compile() Caching Overhead Measurement\n**Learning:** While pre-compiling regular expressions using `re.compile()` at the module level is idiomatic and visually cleaner, benchmarking shows negligible runtime difference (often under 1ms or lost in noise) for functions that compile a static string once per *call* (rather than per-iteration in a loop) because Python internally memoizes recently compiled patterns (up to 512 entries). This makes hoisting them purely a style improvement rather than a critical performance optimization.\n**Action:** When extracting `re.compile()` calls to module constants, document them as style or idiomatic improvements rather than making unverified claims about significant performance overhead.

scripts/ci/implementation_completeness_scan.py

@@ -10,6 +10,8 @@
 from pathlib import Path
 from typing import Iterable
 
+RUST_FN_PATTERN = re.compile(r"\bfn\s+([A-Za-z_][A-Za-z0-9_]*)")
+RUST_MACRO_PATTERN = re.compile(r"\b(todo|unimplemented)\s*!")
 
 RUNTIME_TEST_PARTS = {
     "test",
@@ -249,11 +251,10 @@ def rust_code_lines(source: str) -> list[tuple[int, str]]:
 
 def nearest_rust_symbol(code_lines: list[tuple[int, str]], line_no: int) -> str:
     """Return the nearest preceding Rust function name for a finding."""
-    fn_pattern = re.compile(r"\bfn\s+([A-Za-z_][A-Za-z0-9_]*)")
     for current_line_no, code in reversed(code_lines):
         if current_line_no > line_no:
             continue
-        match = fn_pattern.search(code)
+        match = RUST_FN_PATTERN.search(code)
         if match:
             return match.group(1)
     return "rust module"
@@ -264,9 +265,8 @@ def scan_rust_file(repo_root: Path, relative_path: Path) -> list[Finding]:
     source_path = repo_root / relative_path
     code_lines = rust_code_lines(source_path.read_text(encoding="utf-8"))
     findings: list[Finding] = []
-    macro_pattern = re.compile(r"\b(todo|unimplemented)\s*!")
     for line_no, code in code_lines:
-        for match in macro_pattern.finditer(code):
+        for match in RUST_MACRO_PATTERN.finditer(code):
             macro_name = match.group(1)
             findings.append(
                 Finding(
@@ -305,7 +305,9 @@ def scan_changed_paths(
     return findings, errors
 
 
-def render_report(findings: list[Finding], errors: list[str], checked_count: int) -> str:
+def render_report(
+    findings: list[Finding], errors: list[str], checked_count: int
+) -> str:
     """Render a markdown report for CI logs and review evidence."""
     lines = [
         "# Implementation Completeness Scan",