fix: harden Claro diagnostics and runtime guards

Preserve source locations, validate malformed JSON, and add opt-in resource limits. Include executable error-guide coverage, learner pilot materials, native Windows acceptance helpers, and updated CI/documentation.

tools/validate_error_guide.py

@@ -0,0 +1,25 @@
+#!/usr/bin/env python3
+"""Execute every error-guide failure and repair against the actual interpreter."""
+from pathlib import Path
+import json, os, re, shlex, subprocess, tempfile
+ROOT = Path(__file__).resolve().parents[1]
+def main():
+    cases = json.loads((ROOT/'tests/error_examples.json').read_text())
+    guide = (ROOT/'docs/ERRORS.md').read_text()
+    blocks = re.findall(r'```claro\n(.*?)```',guide,re.S)
+    expected = [c[k] for c in cases for k in ['code','repair']]
+    assert blocks == expected, 'Every error and repair block must match executable coverage'
+    with tempfile.TemporaryDirectory(prefix='claro-error-guide-',dir=os.environ.get('TMPDIR')) as tmp:
+        work=Path(tmp); override=os.environ.get('CLARO_EXE'); exe=Path(override).resolve() if override else work/'claro'
+        if not override:
+            subprocess.run(shlex.split(os.environ.get('CLARO_CC','gcc'))+['-std=c89','-pedantic-errors',str(ROOT/'src/claro.c'),'-o',str(exe),'-lm'],check=True)
+        for case in cases:
+            path=work/case['filename'];path.write_text(case['code'])
+            cmd=[str(exe)]+(['check'] if case['mode']=='check' else [])+[path.name]
+            r=subprocess.run(cmd,cwd=work,capture_output=True,text=True,timeout=10)
+            assert r.returncode==1 and case['diagnostic'] in r.stdout+r.stderr,(case['name'],r.stdout,r.stderr)
+            assert case['diagnostic'] in guide
+            path.write_text(case['repair']);r=subprocess.run([str(exe),path.name],cwd=work,capture_output=True,text=True,timeout=10)
+            assert r.returncode==0 and r.stdout==case['output'],(case['name'],r.stdout,r.stderr)
+            print('PASS error guide:',case['name'])
+if __name__=='__main__':main()