feat(registry): add generate-registry.sh script and docs

Shell script reads .pkg ZIPs, extracts manifests, and emits a
registry.json for self-hosted package discovery. Docs cover the
JSON format, admin config, and self-hosting setup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/generate-registry.sh

@@ -0,0 +1,81 @@
+#!/usr/bin/env bash
+# generate-registry.sh — Build a registry.json from a directory of .pkg files.
+#
+# Usage:
+#   ./scripts/generate-registry.sh [PKG_DIR] [BASE_URL]
+#
+# Arguments:
+#   PKG_DIR   Directory containing .pkg files (default: dist/)
+#   BASE_URL  HTTPS base URL for download links (default: https://example.com/packages)
+#
+# Output:
+#   Writes registry.json to stdout. Redirect to a file:
+#     ./scripts/generate-registry.sh dist/ https://cdn.example.com/pkg > registry.json
+
+set -euo pipefail
+
+PKG_DIR="${1:-dist}"
+BASE_URL="${2:-https://example.com/packages}"
+
+# Strip trailing slash
+BASE_URL="${BASE_URL%/}"
+
+if [ ! -d "$PKG_DIR" ]; then
+    echo "Error: directory '$PKG_DIR' not found" >&2
+    exit 1
+fi
+
+# Collect entries
+entries=()
+
+for pkg in "$PKG_DIR"/*.pkg; do
+    [ -f "$pkg" ] || continue
+
+    # Extract manifest.json from the ZIP archive
+    manifest=$(unzip -p "$pkg" manifest.json 2>/dev/null) || {
+        echo "Warning: skipping $pkg (no manifest.json)" >&2
+        continue
+    }
+
+    # Read fields from manifest
+    id=$(echo "$manifest"          | jq -r '.id // empty')
+    title=$(echo "$manifest"       | jq -r '.title // .id')
+    version=$(echo "$manifest"     | jq -r '.version // "0.0.0"')
+    description=$(echo "$manifest" | jq -r '.description // ""')
+    author=$(echo "$manifest"      | jq -r '.author // ""')
+    type=$(echo "$manifest"        | jq -r '.type // "extension"')
+    tier=$(echo "$manifest"        | jq -r '.tier // "community"')
+
+    if [ -z "$id" ]; then
+        echo "Warning: skipping $pkg (no id in manifest)" >&2
+        continue
+    fi
+
+    filename=$(basename "$pkg")
+    size=$(stat -c%s "$pkg" 2>/dev/null || stat -f%z "$pkg" 2>/dev/null || echo 0)
+    updated_at=$(date -r "$pkg" -u +"%Y-%m-%dT%H:%M:%SZ" 2>/dev/null || date -u +"%Y-%m-%dT%H:%M:%SZ")
+
+    entry=$(jq -n \
+        --arg id "$id" \
+        --arg title "$title" \
+        --arg version "$version" \
+        --arg description "$description" \
+        --arg author "$author" \
+        --arg type "$type" \
+        --arg tier "$tier" \
+        --arg download_url "$BASE_URL/$filename" \
+        --argjson size "$size" \
+        --arg updated_at "$updated_at" \
+        '{id: $id, title: $title, version: $version, description: $description,
+          author: $author, type: $type, tier: $tier, download_url: $download_url,
+          size: $size, updated_at: $updated_at}')
+
+    entries+=("$entry")
+done
+
+# Build final JSON
+if [ ${#entries[@]} -eq 0 ]; then
+    echo '{"packages": []}' | jq .
+else
+    printf '%s\n' "${entries[@]}" | jq -s '{packages: .}'
+fi