feat: report --diff-only — colored terminal diff view

Shows only the changed parts of the latest report: text diffs with
ANSI colors (+green/-red/@cyan), new/missing URLs, link diffs,
hidden content, meta-refresh and inline script findings.
Colors are suppressed when stdout is not a terminal (pipes, log files).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scanner/__main__.py

@@ -1061,8 +1061,83 @@ def cmd_approve(args: argparse.Namespace, cfg: dict) -> int:
     return 1
 
 
+def _print_diff_only(report: dict) -> None:
+    """Print a compact colored diff view of the latest report."""
+    a = report.get("assessment", {})
+    d = report.get("diff", {})
+    level = a.get("level", "green")
+    symbol, _ = ampel(level)
+    use_color = sys.stdout.isatty()
+
+    if use_color:
+        C = {"add": "\033[32m", "del": "\033[31m", "hdr": "\033[36m",
+             "url": "\033[1;34m", "rst": "\033[0m"}
+    else:
+        C = {k: "" for k in ("add", "del", "hdr", "url", "rst")}
+
+    print(f"{symbol}  Level: {level.upper()}   Score: {a.get('score', 0)}")
+    print()
+
+    for domain in d.get("new_external_domains", []):
+        print(f"{C['del']}+ Neue externe Domain: {domain}{C['rst']}")
+    for url in d.get("new_internal_urls", []):
+        print(f"{C['add']}+ Neue URL: {url}{C['rst']}")
+    for url in d.get("missing_internal_urls", []):
+        print(f"{C['del']}- Fehlende URL: {url}{C['rst']}")
+    for entry in d.get("new_broken_urls", []):
+        print(f"{C['del']}! Neuer kaputt Link [{entry['status']}]: {entry['url']}{C['rst']}")
+
+    has_page_diffs = False
+    for pd in d.get("page_diffs", []):
+        text_diff = pd.get("text_diff", [])
+        link_diff = pd.get("link_diff", {})
+        new_hidden = pd.get("new_hidden_content", [])
+        new_refresh = pd.get("new_meta_refresh", [])
+        new_scripts = pd.get("new_inline_scripts", [])
+        new_comments = pd.get("new_comment_links", [])
+        if not (text_diff or link_diff or new_hidden or new_refresh
+                or new_scripts or new_comments or pd.get("canonical_changed")):
+            continue
+        has_page_diffs = True
+        print(f"\n{C['url']}{'─' * 4} {pd['url']} {'─' * 4}{C['rst']}")
+        for line in text_diff:
+            if line.startswith("+"):
+                print(f"{C['add']}{line}{C['rst']}")
+            elif line.startswith("-"):
+                print(f"{C['del']}{line}{C['rst']}")
+            elif line.startswith("@"):
+                print(f"{C['hdr']}{line}{C['rst']}")
+            else:
+                print(line)
+        for ltype, ld in link_diff.items():
+            for added in ld.get("added", []):
+                print(f"{C['add']}+ [{ltype}] {added}{C['rst']}")
+            for removed in ld.get("removed", []):
+                print(f"{C['del']}- [{ltype}] {removed}{C['rst']}")
+        for h in new_hidden:
+            print(f"{C['del']}! Hidden Content ({h.get('type')}): "
+                  f"{', '.join(h.get('indicators', []))}{C['rst']}")
+        for mr in new_refresh:
+            print(f"{C['del']}! Meta-Refresh → {mr}{C['rst']}")
+        if pd.get("canonical_changed"):
+            print(f"{C['del']}! Canonical: {pd.get('old_canonical')} → {pd.get('new_canonical')}{C['rst']}")
+        for s in new_scripts:
+            print(f"{C['del']}! Inline-Script: {', '.join(s.get('patterns', []))}{C['rst']}")
+        for cl in new_comments:
+            print(f"{C['del']}! Kommentar-Link: {cl}{C['rst']}")
+
+    nothing = (
+        not d.get("new_external_domains")
+        and not d.get("new_internal_urls")
+        and not d.get("missing_internal_urls")
+        and not d.get("new_broken_urls")
+        and not has_page_diffs
+    )
+    if nothing:
+        print("Keine Änderungen.")
+
+
 def cmd_report(args: argparse.Namespace, cfg: dict) -> int:
-    fmt = getattr(args, "format", "md")
     rd = Path(cfg["reports_dir"])
     if not rd.exists():
         print("Noch keine Reports vorhanden.")
@@ -1074,11 +1149,17 @@ def cmd_report(args: argparse.Namespace, cfg: dict) -> int:
         return 0
 
     latest = dirs[-1]
-    if fmt == "json":
-        p = latest / "report.json"
-    else:
-        p = latest / "report.md"
 
+    if getattr(args, "diff_only", False):
+        p = latest / "report.json"
+        if not p.exists():
+            print(f"Report-Datei nicht gefunden: {p}", file=sys.stderr)
+            return 1
+        _print_diff_only(json.loads(p.read_text(encoding="utf-8")))
+        return 0
+
+    fmt = getattr(args, "format", "md")
+    p = latest / ("report.json" if fmt == "json" else "report.md")
     if not p.exists():
         print(f"Report-Datei nicht gefunden: {p}", file=sys.stderr)
         return 1
@@ -1379,6 +1460,8 @@ def _build_parser() -> argparse.ArgumentParser:
 
     rp = sub.add_parser("report", help="Letzten Report anzeigen")
     rp.add_argument("--format", choices=["md", "json"], default="md")
+    rp.add_argument("--diff-only", action="store_true",
+                    help="Nur Textdiffs geänderter Seiten anzeigen (farbig)")
 
     sub.add_parser("status", help="Übersichtsstatus anzeigen")