feat(propose): --outline-run selects Arm D, default 0 is off

tools/okf_propose_segments.py

@@ -604,6 +604,11 @@ def run(
             f"--max-segment-chars {max_segment_chars} is negative; the cap is a "
             "character count, and 0 means off (Arm B)"
         )
+    if outline_run < 0:
+        raise ProposerError(
+            f"--outline-run {outline_run} is negative; the gate is a run LENGTH, "
+            "and 0 means off (Arm B)"
+        )
     # Reduced HERE, before anything is read: a prefix that survives to the
     # entries as an empty component would produce exactly the unscoped paths
     # the caller asked to avoid, and would do it silently.
@@ -693,6 +698,23 @@ def parse_args(argv: list[str] | None) -> argparse.Namespace:
             "the K3 method file"
         ),
     )
+    parser.add_argument(
+        "--outline-run",
+        type=int,
+        default=0,
+        metavar="N",
+        help=(
+            "Arm D: also propose a boundary at each line of the document's own "
+            "numbered outline (the bare integers the heading grammar cannot "
+            "match, since it requires a dot), but only where those integers "
+            "sustain an ascending run of at least N entries, and only for the "
+            "LAST such run when the outline repeats, because a contents listing "
+            "precedes the body it lists. 0 (the default) is OFF and leaves the "
+            "artifact byte-identical to Arm B. Arm D is the author's definition, "
+            "written for order 20260906T213322Z; it is not defined upstream, and "
+            "the K3 method file does not name it either"
+        ),
+    )
     parser.add_argument(
         "--proposed-at",
         default="1970-01-01T00:00:00Z",
@@ -711,6 +733,7 @@ def main(argv: list[str] | None = None) -> int:
             proposed_at=args.proposed_at,
             path_prefix=args.path_prefix,
             max_segment_chars=args.max_segment_chars,
+            outline_run=args.outline_run,
         )
     except ProposerError as exc:
         print(f"{PROPOSER_ID}: FAILED - {exc}", file=sys.stderr)