refactor(opencode): restructure config and replace legacy plugins

Rewrites opencode.json, drops the with-context, websearch and terminal-bell
plugins, adds plugins that strip Claude-only commands and OMC MCP servers,
and vendors the impeccable, web-design-guidelines and frontend-workflow skills.

.config/opencode/plugin/lib/claude-only-command-registry.ts

@@ -0,0 +1,55 @@
+type PrefixRule = {
+  readonly kind: "prefix"
+  readonly prefix: string
+  readonly reason: string
+}
+
+type ExactRule = {
+  readonly kind: "exact"
+  readonly name: string
+  readonly reason: string
+}
+
+export type ClaudeOnlyCommandRule = PrefixRule | ExactRule
+
+export const CLAUDE_ONLY_COMMAND_RULES: readonly ClaudeOnlyCommandRule[] = [
+  {
+    kind: "prefix",
+    prefix: "oh-my-claudecode:",
+    reason: "Operates the Oh My ClaudeCode runtime and workflows.",
+  },
+  {
+    kind: "prefix",
+    prefix: "claude-notifications-go:",
+    reason: "Configures notification hooks, binaries, and files for Claude Code.",
+  },
+  {
+    kind: "exact",
+    name: "remember:doctor",
+    reason: "Executes diagnostics through CLAUDE_PLUGIN_ROOT; remember:remember stays because it supports multiple agent hosts.",
+  },
+  {
+    kind: "exact",
+    name: "mcp-server-dev:build-mcpb",
+    reason: "Produces Anthropic MCPB bundles with claude_desktop compatibility; the server and app builders stay because they target multiple MCP hosts.",
+  },
+] as const
+
+function matchesRule(name: string, rule: ClaudeOnlyCommandRule): boolean {
+  switch (rule.kind) {
+    case "prefix":
+      return name.startsWith(rule.prefix)
+    case "exact":
+      return name === rule.name
+    default:
+      return assertNever(rule)
+  }
+}
+
+function assertNever(value: never): never {
+  throw new Error(`Unhandled rule: ${JSON.stringify(value)}`)
+}
+
+export function isClaudeOnlyCommand(name: string): boolean {
+  return CLAUDE_ONLY_COMMAND_RULES.some((rule) => matchesRule(name, rule))
+}