fix(s03,s04,s20): remove dead safe_path, sync READMEs

- Delete safe_path entirely (following PR #483 approach) — no dead code
- Update all 3 READMEs per module to reflect read_file in Gate 2
- s04: also update permission_hook snippet in READMEs
- s20: remove safe_path (already replaced with inline resolution)

Closes #482

s03_permission/README.en.md

@@ -61,7 +61,7 @@ PERMISSION_RULES = [
     {
         "tools": ["read_file", "write_file", "edit_file"],
         "check": lambda args: not (WORKDIR / args.get("path", "")).resolve().is_relative_to(WORKDIR),
-        "message": "Writing outside workspace",
+        "message": "Access outside workspace",
     },
     {
         "tools": ["bash"],

s03_permission/README.ja.md

@@ -61,7 +61,7 @@ PERMISSION_RULES = [
     {
         "tools": ["read_file", "write_file", "edit_file"],
         "check": lambda args: not (WORKDIR / args.get("path", "")).resolve().is_relative_to(WORKDIR),
-        "message": "Writing outside workspace",
+        "message": "Access outside workspace",
     },
     {
         "tools": ["bash"],

s03_permission/README.md

@@ -61,7 +61,7 @@ PERMISSION_RULES = [
     {
         "tools": ["read_file", "write_file", "edit_file"],
         "check": lambda args: not (WORKDIR / args.get("path", "")).resolve().is_relative_to(WORKDIR),
-        "message": "Writing outside workspace",
+        "message": "Access outside workspace",
     },
     {
         "tools": ["bash"],