chore(l10n): add CI guard against ARB placeholder corruption

Adds tool/check_arb_placeholder_corruption.py, a static check that flags
literal "?" glued to an ICU placeholder brace in any lib/l10n/app_*.arb
value that has a placeholders metadata block. This is the exact corruption
shape fixed in the previous commit; flutter analyze doesn't catch it since
the JSON/ICU stays syntactically valid. Wired as a CI step before
flutter analyze so it fails fast.

Also audited lib/l10n/app_localizations_ext.dart (hand-maintained weekday/
month/date-sentence maps, not covered by ARB tooling): all 22 locale maps
have the full 13/13 keys with no corruption or leftover English — no
changes needed there.

.gitea/workflows/build.yml

@@ -27,6 +27,9 @@ jobs:
       - name: Obtener dependencias
         run: flutter pub get
 
+      - name: Verificar integridad de literales i18n
+        run: python3 tool/check_arb_placeholder_corruption.py
+
       - name: Analizar código
         run: flutter analyze --no-fatal-infos --no-fatal-warnings
 

tool/check_arb_placeholder_corruption.py

@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+"""Detect corrupted ICU placeholders in ARB localization files.
+
+Guards against the class of bug where a translation string value gets a
+literal '?' glued next to an ICU placeholder brace (e.g. "{hours}??
+{minutes}?"), silently destroying the translated text while staying valid
+JSON/ICU. This does not require Flutter tooling, so it can run early and
+fast in CI.
+"""
+
+from __future__ import annotations
+
+import glob
+import json
+import re
+import sys
+from pathlib import Path
+
+# A literal '?' sitting immediately adjacent (0-1 whitespace chars) to a
+# placeholder brace. Narrow on purpose: a normal sentence ending in a real
+# '?' does not sit glued to a '{' or '}', so it won't match.
+CORRUPTION_PATTERN = re.compile(r"\}\s?\?|\?\s?\{")
+
+ARB_GLOB = "lib/l10n/app_*.arb"
+
+
+def find_repo_root(start: Path) -> Path:
+    """Walk up from `start` until a directory containing lib/l10n is found."""
+    current = start.resolve()
+    for candidate in [current, *current.parents]:
+        if (candidate / "lib" / "l10n").is_dir():
+            return candidate
+    return current
+
+
+def check_file(path: Path) -> list[str]:
+    """Return a list of human-readable findings for a single ARB file."""
+    findings: list[str] = []
+
+    try:
+        raw = path.read_text(encoding="utf-8")
+    except UnicodeDecodeError as exc:
+        return [f"{path}: FAILED TO DECODE AS UTF-8 -> {exc}"]
+
+    try:
+        data = json.loads(raw)
+    except json.JSONDecodeError as exc:
+        return [f"{path}: FAILED TO PARSE JSON -> {exc}"]
+
+    for key, value in data.items():
+        if key.startswith("@"):
+            continue
+
+        meta = data.get(f"@{key}")
+        if not isinstance(meta, dict) or "placeholders" not in meta:
+            continue
+
+        if not isinstance(value, str):
+            continue
+
+        if CORRUPTION_PATTERN.search(value):
+            findings.append(f'{path}:{key} -> "{value}"')
+
+    return findings
+
+
+def main() -> int:
+    repo_root = find_repo_root(Path(__file__).parent)
+    arb_files = sorted(glob.glob(str(repo_root / ARB_GLOB)))
+
+    if not arb_files:
+        print(f"No ARB files found matching {ARB_GLOB} under {repo_root}")
+        return 1
+
+    all_findings: list[str] = []
+    for arb_path in arb_files:
+        all_findings.extend(check_file(Path(arb_path)))
+
+    if all_findings:
+        print("Placeholder corruption detected in ARB files:")
+        for finding in all_findings:
+            print(f"  {finding}")
+        print(f"\n{len(all_findings)} finding(s) across {len(arb_files)} file(s).")
+        return 1
+
+    print(f"OK: checked {len(arb_files)} ARB file(s), no placeholder corruption found.")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())