Merge pull request 'fix(re): the capture-citation check was red on a clean tree' (#65) from fix/captures-root-citation into main

Reviewed-on: #65

tools/re/check-capture-citations

@@ -82,10 +82,16 @@ def committed() -> tuple[set[str], set[str]]:
             if fn == ".gitignore":
                 continue
             files.add(os.path.join(dirpath, fn).replace(os.sep, "/"))
+    # 🔴 START AT 3, NOT 4 — 3 is `docs/re/captures` ITSELF. Starting at 4 built
+    # every sub-directory and never the root, so the eight pages that cite the
+    # directory as a whole ("evidence lives in `docs/re/captures/`") each looked
+    # like a citation of a file that does not exist, and the gate was red on a
+    # clean, correct tree. The selftest could not see it either: it took an
+    # arbitrary member of `dirs`, which is always a sub-directory.
     dirs = set()
     for f in files:
         parts = f.split("/")
-        for i in range(4, len(parts)):          # docs/re/captures/<dir>/...
+        for i in range(3, len(parts)):          # docs/re/captures[/<dir>/...]
             dirs.add("/".join(parts[:i]) + "/")
     return files, dirs
 
@@ -182,6 +188,9 @@ def selftest() -> int:
         ("real file passed", real_file, True),
         ("directory reference passed", real_dir, True),
         ("directory without slash passed", real_dir.rstrip("/"), True),
+        # The root is the case the arbitrary `real_dir` above can never be.
+        ("captures root itself passed", ROOT, True),
+        ("captures root without slash passed", ROOT.rstrip("/"), True),
         ("sentence punctuation stripped", real_file + ".", True),
     ]
     # 🔴 THE SELFTEST USED TO PASS WHILE THE SCAN RETURNED NOTHING. It exercised