fix: graceful regex-only fallback when GLiNER unavailable

Prevent a hard crash (ModuleNotFoundError: gliner) when GLiNER isn't
installed locally, and reduce regex false positives.

- redac/detect.py: add gliner_available(); skip the GLiNER path and run
regex-only when it can't be imported. Phone recognizer now ignores dates
and digit runs shorter than 7 digits (serial numbers).
- app.py: show a warning banner when running in regex-only mode.

On the Space, GLiNER is installed so full NER runs; locally the app no
longer errors.

Co-authored-by: OpenAI Codex <codex@openai.com>

app.py

@@ -19,6 +19,14 @@ from redac import (
     extract_text_from_image,
     DEFAULT_LABELS,
 )
+from redac.detect import gliner_available
+
+_NER_NOTE = (
+    "" if gliner_available()
+    else "\n\n> ⚠️ GLiNER not installed: running **regex-only** (structured "
+    "IDs like email/phone/IBAN). Names, addresses and other free-text PII "
+    "need GLiNER, which is available on the Space."
+)
 
 EXAMPLE = (
     "Patient John A. Doe, DOB 1985-04-12, was admitted on 2026-06-01. "
@@ -57,7 +65,7 @@ with gr.Blocks(title="Redac") as demo:
     gr.Markdown(
         "# 🖍️ Redac\n"
         "**A local privacy gateway.** Detect and redact PII *before* it reaches "
-        "a downstream model. Reversible: the mapping stays local."
+        "a downstream model. Reversible: the mapping stays local." + _NER_NOTE
     )
 
     with gr.Tabs():

redac/detect.py

@@ -71,9 +71,12 @@ def _regex_entities(text: str) -> List[Entity]:
             span = m.group().strip()
             if len(span) < 4:
                 continue
-            # Don't let the phone recognizer misfire on dates.
-            if label == "phone number" and _DATE_RE.match(span):
-                continue
+            # Phone recognizer: ignore dates and short digit runs (serials).
+            if label == "phone number":
+                if _DATE_RE.match(span):
+                    continue
+                if sum(c.isdigit() for c in span) < 7:
+                    continue
             out.append(
                 Entity(
                     start=m.start(),
@@ -89,6 +92,18 @@ def _regex_entities(text: str) -> List[Entity]:
 
 # --- GLiNER ------------------------------------------------------------------
 
+@lru_cache(maxsize=1)
+def gliner_available() -> bool:
+    """True if GLiNER can be imported. Lets the app fall back to regex-only
+    (and tell the user) instead of crashing when GLiNER isn't installed."""
+    try:
+        import gliner  # noqa: F401
+
+        return True
+    except Exception:
+        return False
+
+
 @lru_cache(maxsize=1)
 def _load_gliner():
     from gliner import GLiNER
@@ -137,6 +152,6 @@ def detect_entities(
         return []
     labels = labels or DEFAULT_LABELS
     found: List[Entity] = _regex_entities(text)
-    if use_gliner:
+    if use_gliner and gliner_available():
         found.extend(_gliner_entities(text, labels, threshold))
     return _resolve_overlaps(found)