Release 0.18.5: bump VERSION + metadata.json

Align the Python package / PCM metadata with rust_router 0.18.5 (already bumped
during the bus-corridor + soft-knobs wave: 0.18.4 cross-layer bus attraction
+ multiplicative discount #296-R9-B, 0.18.5 P3 attraction-field precompute).
Cargo.toml / Cargo.lock / rust_router/README.md were already at 0.18.5 and are
untouched here; the built grid_router.so reports __version__ = 0.18.5.

metadata.json download_url -> v0.18.5 asset; status stays "testing";
sha256/size remain placeholders (filled by the PCM publish step).

Parity: 143d097..9473bf8 audited and CONFIRMED (see .gui-parity-checked),
with the --zone-clearance converter fix (9466342) in this release.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CYo8MbrsBUq4DCkU9nwm3j

Author: drandyhaas

VERSION

@@ -1 +1 @@
-0.18.3
+0.18.5

metadata.json

@@ -25,7 +25,7 @@
   ],
   "versions": [
     {
-      "version": "0.18.3",
+      "version": "0.18.5",
       "status": "testing",
       "kicad_version": "9.0",
       "runtime": "swig",
@@ -34,7 +34,7 @@
         "macos",
         "windows"
       ],
-      "download_url": "https://github.com/drandyhaas/KiCadRoutingTools/releases/download/v0.18.3/KiCadRoutingTools-0.18.3.zip",
+      "download_url": "https://github.com/drandyhaas/KiCadRoutingTools/releases/download/v0.18.5/KiCadRoutingTools-0.18.5.zip",
       "download_sha256": "0000000000000000000000000000000000000000000000000000000000000000",
       "download_size": 0,
       "install_size": 0