Exclude .pnpm-store from Biome and add .dockerignore

The CI runner's pnpm store lands inside the workspace, causing
Biome to lint/format hundreds of store index JSON files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,9 @@
+node_modules
+.pnpm-store
+dist
+coverage
+.git
+.claude
+.specify
+specs
+docs

biome.json

@@ -7,7 +7,8 @@
 			"!.claude/**",
 			"!.specify/**",
 			"!specs/**",
-			"!coverage/**"
+			"!coverage/**",
+			"!.pnpm-store/**"
 		]
 	},
 	"assist": {