fix: macOS portability — pure --json stdout for the SynthID scorer, BSD realpath probe (#70)

* fix: keep the SynthID scorer's --json stdout pure

The reverse-SynthID upstream prints progress ('CodebookV4 loaded: ...')
straight to stdout. image_meta.py parses the scorer's stdout with
json.loads, so the leak corrupts every score payload into
{'available': False, 'error': 'bad scorer JSON: ...'}.

Redirect stdout to stderr around the upstream calls so --json owns
stdout. Regression test drives the real script against a deliberately
noisy stub upstream (with a stub cv2, so it runs without OpenCV).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* fix: probe realpath -m support instead of realpath presence

macOS ships BSD realpath, which exists but has no -m flag, so
'command -v realpath' takes the GNU branch and both setup bootstraps
abort on the first path they normalize. Probe the flag itself; BSD
systems fall through to the portable pwd fallback already in place.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

---------

Co-authored-by: Adriel <adriel@Adriels-MacBook-Pro-2026.local>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
Co-authored-by: Guillaume Meyer (The Opinionated Man) <1385518+guillaumemeyer@users.noreply.github.com>

service/scripts/score_synthid.py

@@ -16,6 +16,7 @@ Exit codes:
 from __future__ import annotations
 
 import argparse
+import contextlib
 import json
 import os
 import sys
@@ -90,13 +91,17 @@ def main() -> int:
             return 2
         rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
 
-        codebook_v4 = SpectralCodebookV4()
-        codebook_v4.load(str(codebook))
+        # Upstream prints progress ("CodebookV4 loaded: ...") straight to
+        # stdout, which corrupts --json for any caller that parses us
+        # (image_meta.py json.loads our stdout). Keep stdout ours alone.
+        with contextlib.redirect_stdout(sys.stderr):
+            codebook_v4 = SpectralCodebookV4()
+            codebook_v4.load(str(codebook))
 
-        extractor = RobustSynthIDExtractor()
-        result = extractor.detect_from_v4_codebook(
-            rgb, codebook_v4, model=args.model
-        )
+            extractor = RobustSynthIDExtractor()
+            result = extractor.detect_from_v4_codebook(
+                rgb, codebook_v4, model=args.model
+            )
     except Exception as e:
         print(f"scorer error: {e}", file=sys.stderr)
         return 1

service/scripts/setup_ctrlregen.sh

@@ -58,7 +58,7 @@ done
 
 DIR="${DIR:-$DEFAULT_DIR}"
 mkdir -p "$(dirname "$DIR")"
-if command -v realpath >/dev/null 2>&1; then
+if realpath -m . >/dev/null 2>&1; then  # BSD/macOS realpath has no -m
   DIR="$(realpath -m "$DIR")"
 else
   DIR="$(cd "$(dirname "$DIR")" && pwd)/$(basename "$DIR")"

service/scripts/setup_synthid.sh

@@ -63,7 +63,7 @@ done
 
 DIR="${DIR:-$DEFAULT_DIR}"
 mkdir -p "$(dirname "$DIR")"
-if command -v realpath >/dev/null 2>&1; then
+if realpath -m . >/dev/null 2>&1; then  # BSD/macOS realpath has no -m
   DIR="$(realpath -m "$DIR")"
 else
   DIR="$(cd "$(dirname "$DIR")" && pwd)/$(basename "$DIR")"