feat: dossiers-ngi sticky bar vs-main +green/−red diffstat

scripts/dossiers-ngi/README.md

@@ -58,6 +58,7 @@ Per branch in JSON / sticky bar:
 | `tip_time` | committer time of tip (`%cI`) |
 | `built_at` | when this edition freeze was written |
 | `build_seconds` | wall time of that freeze |
+| `vs_main_plus` / `vs_main_minus` | `git diff --numstat` tip vs `main` tip (sticky bar +grün/−rot; omitted on `main`) |
 
 Rebuild runs **only when** `.edition-tip` ≠ current tip (timer never forces).
 Each run also: `git fetch --prune`, `worktree prune`, drop stale

scripts/dossiers-ngi/branch-status-hourly.py

@@ -234,6 +234,30 @@ def tip_recorded(editions: Path, slug: str) -> str:
     return p.read_text(encoding="utf-8").strip()
 
 
+
+def diff_vs_main(repo: Path, main_tip: str, tip: str) -> tuple[int, int]:
+    """Insertions/deletions of tip vs main tip (git diff --numstat)."""
+    if not main_tip or not tip or main_tip == tip:
+        return 0, 0
+    cp = git(repo, "diff", "--numstat", main_tip, tip, check=False)
+    if cp.returncode != 0:
+        return 0, 0
+    plus = minus = 0
+    for line in (cp.stdout or "").splitlines():
+        parts = line.split("	")
+        if len(parts) < 3:
+            continue
+        a, d = parts[0], parts[1]
+        if a == "-" or d == "-":
+            continue
+        try:
+            plus += int(a)
+            minus += int(d)
+        except ValueError:
+            continue
+    return plus, minus
+
+
 def tip_commit_time(repo: Path, tip: str) -> str:
     """Committer ISO time of tip (empty on failure)."""
     cp = git(repo, "log", "-1", "--format=%cI", tip, check=False)
@@ -531,6 +555,10 @@ def build_payload(repo: Path, tips: dict[str, str], rebuild: bool) -> dict:
             sync_flask_alias(ed_root, tips)
 
     tip_times = {name: tip_commit_time(repo, tip) for name, tip in tips.items()}
+    main_tip = tips.get("main", "")
+    vs_main = {
+        name: diff_vs_main(repo, main_tip, tip) for name, tip in tips.items()
+    }
     branches_out = []
     for row in rows:
         name = row["branch"]
@@ -556,6 +584,11 @@ def build_payload(repo: Path, tips: dict[str, str], rebuild: bool) -> dict:
             entry["built_at"] = meta["built_at"]
         if "build_seconds" in meta:
             entry["build_seconds"] = meta["build_seconds"]
+        # sticky bar: +grün / −rot vs main (omit on main itself)
+        if name != "main" and main_tip:
+            plus, minus = vs_main.get(name, (0, 0))
+            entry["vs_main_plus"] = plus
+            entry["vs_main_minus"] = minus
         branches_out.append(entry)
 
     payload = {