build(deps-dev): bump @opencode-ai/plugin from 1.17.13 to 1.18.4

Bumps @opencode-ai/plugin from 1.17.13 to 1.18.4.

---
updated-dependencies:
- dependency-name: "@opencode-ai/plugin"
  dependency-version: 1.18.4
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

bun.lock

@@ -28,7 +28,7 @@
     "@earendil-works/pi-ai": "0.80.3",
     "@earendil-works/pi-coding-agent": "0.80.3",
     "@earendil-works/pi-tui": "0.80.3",
-    "@opencode-ai/plugin": "1.17.13",
+    "@opencode-ai/plugin": "1.18.4",
     "@tsconfig/bun": "1.0.10",
     "@types/bun": "1.3.14",
     "dedent": "^1.7.2",