--promote-failures: reroute with the connections that failed moved first

Each round routes every connection that has failed so far ahead of the
rest, which keep their order. The promoted set only grows, so two groups
cannot take turns failing; the best round is kept.

src/freeroute/route/pipeline.py

@@ -81,6 +81,7 @@ def route_dsn_board(
     rip_up: bool = True,
     max_passes: int = 10,
     seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> tuple[RouteResult, int, list[str]]:
     """Route a parsed :class:`DsnBoard`; return the board-unit result, the scale,
     and the layer names. ``layers`` restricts routing to those signal-layer
@@ -102,6 +103,7 @@ def route_dsn_board(
         rip_up=rip_up,
         max_passes=max_passes,
         seed=seed,
+        route_first=route_first,
     )
     return result, scale, [layer.name for layer in dsn.layers]
 
@@ -143,11 +145,13 @@ def build_routing_result(
     max_passes: int = 10,
     edge_clearance_mm: float | None = None,
     seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> RoutingResult:
     """Route ``dsn`` (grid track) and convert to a DSN-unit RoutingResult."""
     route, scale, layer_names = route_dsn_board(
         dsn, layers=layers, rip_up=rip_up, max_passes=max_passes,
         edge_clearance_mm=edge_clearance_mm, resolution=resolution, seed=seed,
+        route_first=route_first,
     )
     return _to_routing_result(route, dsn, scale, layer_names)
 
@@ -164,6 +168,7 @@ def route_dsn_board_exact(
     shove: bool = False,
     diagonal: bool = False,
     seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> tuple[ExactRouteResult, int, list[str]]:
     """Route a parsed :class:`DsnBoard` with the exact-geometry (orthogonal,
     DRC-verified) track; return the exact result, the scale, and layer names.
@@ -189,6 +194,7 @@ def route_dsn_board_exact(
         shove=shove,
         diagonal=diagonal,
         seed=seed,
+        route_first=route_first,
     )
     return exact, scale, [layer.name for layer in dsn.layers]
 
@@ -205,6 +211,7 @@ def build_exact_routing_result(
     max_passes: int = 10,
     edge_clearance_mm: float | None = None,
     seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> RoutingResult:
     """Route ``dsn`` (exact track) and convert to a DSN-unit RoutingResult."""
     exact, scale, layer_names = route_dsn_board_exact(
@@ -218,6 +225,7 @@ def build_exact_routing_result(
         resolution=resolution,
         heuristic_weight=heuristic_weight,
         seed=seed,
+        route_first=route_first,
     )
     return _to_routing_result(exact.result, dsn, scale, layer_names)