build(deps-dev): bump @solana/kit-plugin-signer from 0.10.0 to 0.12.1 in /clients/js (#1276)

build(deps-dev): bump @solana/kit-plugin-signer in /clients/js

Bumps [@solana/kit-plugin-signer](https://github.com/anza-xyz/kit-plugins) from 0.10.0 to 0.12.1.
- [Commits](https://github.com/anza-xyz/kit-plugins/compare/@solana/kit-plugin-signer@0.10.0...@solana/kit-plugin-signer@0.12.1)

---
updated-dependencies:
- dependency-name: "@solana/kit-plugin-signer"
  dependency-version: 0.12.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]

clients/js/package.json

@@ -59,7 +59,7 @@
         "@solana/kit-plugin-instruction-plan": "^0.12.1",
         "@solana/kit-plugin-litesvm": "^0.10.0",
         "@solana/kit-plugin-rpc": "^0.11.1",
-        "@solana/kit-plugin-signer": "^0.10.0",
+        "@solana/kit-plugin-signer": "^0.12.1",
         "@solana/zk-sdk": "^0.4.2",
         "@types/node": "^26",
         "oxfmt": "^0.56.0",