Fix OpenCode slash command bridge (#483)

Add a first-class OpenCode command bridge across builds, installs, updates, linked installs, and pinned shortcuts. Preserve current provider behavior while backfilling missing or drifted command files.\n\nAI assistance: contributor and maintainer work used AI tools as disclosed in the PR discussion and commits.

scripts/lib/root-commands-sync.mjs

@@ -0,0 +1,27 @@
+/**
+ * Mirror generated provider command files (e.g. OpenCode's
+ * commands/impeccable.md) from dist/ into the tracked root harness folders.
+ * Without this, the release sync ships skills/agents/hooks but no slash
+ * command bridge, so direct GitHub, npx-skills, and submodule installs of
+ * OpenCode stay bridge-less (#483). Per-entry copy like the skills sync:
+ * the destination directory is never removed, so repo-local or pinned
+ * command files are preserved.
+ */
+import fs from 'node:fs';
+import path from 'node:path';
+
+export function syncRootCommands(distDir, rootDir, providers) {
+  const synced = [];
+  for (const { provider, configDir } of providers) {
+    const src = path.join(distDir, provider, configDir, 'commands');
+    if (!fs.existsSync(src)) continue;
+    const dest = path.join(rootDir, configDir, 'commands');
+    fs.mkdirSync(dest, { recursive: true });
+    for (const entry of fs.readdirSync(src, { withFileTypes: true })) {
+      if (!entry.isFile()) continue;
+      fs.copyFileSync(path.join(src, entry.name), path.join(dest, entry.name));
+    }
+    synced.push(configDir);
+  }
+  return synced;
+}