[code-simplifier] Consolidate repo-root helpers and simplify skill script logic (#9772)

This change simplifies recently touched skill scripts by removing
duplicated repo-root discovery code, promoting shared root lookup to a
public API, and tightening small readability issues without changing
behavior. It keeps script semantics intact while making cross-skill
reuse explicit.

- **Shared API cleanup (`.github/skills/shared/z3db.py`)**
  - Promote `_find_repo_root` to public `find_repo_root`.
- Add `require_repo_root()` for scripts that should fail-fast when root
discovery fails.
  - Update library usage docstring to expose both helpers.
- Replace adjacent SQL string literals in `log()` with a single literal.

- **Deduplicate memory-safety root lookup
(`.github/skills/memory-safety/scripts/memory_safety.py`)**
  - Remove local `find_repo_root()` implementation.
  - Import and use shared `require_repo_root()` from `z3db`.

- **Simplify static-analysis label selection
(`.github/skills/static-analysis/scripts/static_analysis.py`)**
  - Replace two-step label assignment with a single expression:
    - `label = f["type"] or f["category"]`

```python
# before
label = f["category"]
if f["type"]:
    label = f["type"]

# after
label = f["type"] or f["category"]
```

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

.github/skills/memory-safety/scripts/memory_safety.py

@@ -18,7 +18,7 @@ import time
 from pathlib import Path
 
 sys.path.insert(0, str(Path(__file__).resolve().parent.parent.parent / "shared"))
-from z3db import Z3DB, setup_logging
+from z3db import Z3DB, require_repo_root, setup_logging
 
 logger = logging.getLogger("z3agent")
 
@@ -52,19 +52,6 @@ def check_dependencies():
         sys.exit(1)
 
 
-def find_repo_root() -> Path:
-    d = Path.cwd()
-    for _ in range(10):
-        if (d / "CMakeLists.txt").exists() and (d / "src").is_dir():
-            return d
-        parent = d.parent
-        if parent == d:
-            break
-        d = parent
-    logger.error("could not locate Z3 repository root")
-    sys.exit(1)
-
-
 def build_is_configured(build_dir: Path, sanitizer: str) -> bool:
     """Check whether the build directory already has a matching cmake config."""
     cache = build_dir / "CMakeCache.txt"
@@ -220,7 +207,7 @@ def main():
 
     setup_logging(args.debug)
     check_dependencies()
-    repo_root = find_repo_root()
+    repo_root = require_repo_root()
 
     sanitizers = ["asan", "ubsan"] if args.sanitizer == "both" else [args.sanitizer]
     all_findings = []