chore: upgrade the neckbeard baseline from v0.1.1 to v0.3.1

Three minor releases at once. Byte-identical surface: only WORKFLOW.md
actually changed (+128/-2); CLAUDE.md and the four templates are
untouched. AGENTS.md takes the new upstream prefix (+22/-2) and keeps our
project section unchanged.

The two declared-extended files were reconciled by hand, because nothing
compares them: validate.py gains upstream's check_vendored_portable, and
schema.yaml gains vendored, project_section_marker, the judged link field
and the ledger and verdict types. gen_status.py needed nothing — upstream
did not touch it. Recorded in the new HERKUNFT.md, including that this
reconciliation has no contradictor and will be forgotten next time.

Newly adopted: check_harvest.py and judge.py, plus docs/ledger/ and
docs/verdict/ with their templates. Deliberately not adopted:
check_locked.py — pruefe_sperrliste.py has done that job here since
2026-08-20, and two tools for one rule is maintenance without gain.

The v0.1.1 baseline stays where it is; docs/sources is immutable.

scripts/validate.py

@@ -161,6 +161,32 @@ def check_body_links(path: Path, body: str, root: Path, inbound: set) -> None:
             inbound.add(target)
 
 
+def check_vendored_portable(root: Path, vendored: list, marker: str) -> None:
+    """Files adopters hold byte-identical must carry no repo-relative link.
+
+    They are copied into repositories without this repo's docs/, so such a
+    link resolves here and nowhere else — and the adoption path in
+    AGENTS.md §5 asks for a byte-for-byte copy, which makes the dead link
+    the adopter's problem and unfixable without breaking the copy.
+    """
+    for rel in vendored or []:
+        path = root / rel
+        if not path.is_file():
+            continue
+        body = path.read_text(encoding="utf-8")
+        if marker and marker in body:
+            # Everything below the marker is the adopting project's own
+            # section: never copied elsewhere, so its links are fine.
+            body = body.split(marker, 1)[0]
+        body = re.sub(r"```.*?```", "", body, flags=re.S)
+        body = re.sub(r"`[^`\n]*`", "", body)
+        for link in (m.group(1) for m in INLINE_LINK_RE.finditer(body)):
+            if link.startswith(EXTERNAL_PREFIXES) or link.startswith("#"):
+                continue
+            err(path, f"vendored file carries a repo-relative link: {link} "
+                      f"— name the target instead of linking to it")
+
+
 def apply_rules(path: Path, rel: str, meta: dict, spec: dict) -> None:
     for rule in spec.get("rules", []):
         if rule == "superseded_requires_pointer":
@@ -184,6 +210,9 @@ def main() -> int:
     link_fields = schema.get("link_fields", [])
     types = schema.get("types", {})
     inbound: set = set()
+
+    check_vendored_portable(root, schema.get("vendored", []),
+                            schema.get("project_section_marker", ""))
     wiki_pages: list[tuple[Path, dict]] = []
 
     # Root documents: inline links must resolve; no frontmatter required.