feat: add lint rule to enforce webview import boundaries

Adds a GritQL-based Biome plugin that enforces architectural separation
between the webview and extension code. The webview should only import
from @shared/* and its own modules, never from extension-only paths.

Blocked imports:
- @core/*
- @hosts/*
- @api/*
- @services/*
- @integrations/*
- @packages/*
- @generated/*

This catches violations at lint time, preventing architectural drift
that could break the gRPC bridge abstraction layer.

biome.jsonc

@@ -131,6 +131,14 @@
 		"src/dev/grit/process-env.grit"
 	],
 	"overrides": [
+		{
+			"includes": [
+				"webview-ui/**"
+			],
+			"plugins": [
+				"src/dev/grit/webview-import-boundary.grit"
+			]
+		},
 		{
 			"includes": [
 				"**",

src/dev/grit/webview-import-boundary.grit

@@ -0,0 +1,33 @@
+// Enforce import boundaries for webview code.
+// The webview should only import from @shared/* and its own modules,
+// never from extension-only paths like @core/*, @hosts/*, @api/*, etc.
+// This maintains the architectural separation between webview and extension.
+
+or {
+	// Regular imports
+	`import $x from $source` where {
+		or {
+			$source <: includes "@core/",
+			$source <: includes "@hosts/",
+			$source <: includes "@api/",
+			$source <: includes "@services/",
+			$source <: includes "@integrations/",
+			$source <: includes "@packages/",
+			$source <: includes "@generated/"
+		},
+		register_diagnostic(span=$source, message="Webview cannot import from extension modules. Use @shared/* for shared types or communicate via gRPC bridge.")
+	},
+	// Type imports
+	`import type $x from $source` where {
+		or {
+			$source <: includes "@core/",
+			$source <: includes "@hosts/",
+			$source <: includes "@api/",
+			$source <: includes "@services/",
+			$source <: includes "@integrations/",
+			$source <: includes "@packages/",
+			$source <: includes "@generated/"
+		},
+		register_diagnostic(span=$source, message="Webview cannot import types from extension modules. Use @shared/* for shared types.")
+	}
+}