Add main entry point + systemd services + integration tests

New files:
  main.py                   - PedalApp: boots all subsystems in order,
                              wires MIDI/footswitch callbacks, graceful
                              teardown reverses boot order
  src/system/config.py      - YAML config loader with deep-merge
                              (separated to avoid hardware deps)
  src/system/services.py    - systemd unit generator for pedal.service
                              + multi-fx-pedal.target
  scripts/install_service.sh - copies project, creates venv, installs
                              + enables service units
  tests/test_integration.py - 41 tests: boot, routing, display sync,
                              teardown, systemd content, CLI, edge cases

Modified:
  tests/conftest.py         - add project root to sys.path

scripts/download_presets.sh

@@ -0,0 +1,159 @@
+#!/usr/bin/env bash
+# ──────────────────────────────────────────────────────────────────────────────
+# download_presets.sh — Factory preset installer for Pi Multi-FX Pedal
+#
+# Downloads and installs the bundled factory presets from the project's
+# GitHub releases or the local source tree into the user preset store.
+#
+# Usage:
+#   ./scripts/download_presets.sh                    # Install from bundled local presets
+#   ./scripts/download_presets.sh --overwrite         # Overwrite existing presets
+#   ./scripts/download_presets.sh --source <url>      # Download from a fallback URL
+#   ./scripts/download_presets.sh --help              # This message
+#
+# The factory presets ship with the project in presets/factory/ as
+# bank_*/preset_*.json files. This script copies them to ~/.pedal/presets/
+# (or PEDAL_CONFIG_DIR if set).
+# ──────────────────────────────────────────────────────────────────────────────
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+
+# Where factory presets live in the source tree
+FACTORY_SOURCE="$PROJECT_ROOT/presets/factory"
+
+# Where the pedal stores presets
+CONFIG_DIR="${PEDAL_CONFIG_DIR:-$HOME/.pedal}"
+PRESET_DIR="$CONFIG_DIR/presets"
+
+OVERWRITE=false
+FALLBACK_URL=""
+
+# ── Parse arguments ─────────────────────────────────────────────────────────
+
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --overwrite)
+            OVERWRITE=true
+            shift
+            ;;
+        --source)
+            if [[ -z "${2:-}" ]]; then
+                echo "ERROR: --source requires a URL argument" >&2
+                exit 1
+            fi
+            FALLBACK_URL="$2"
+            shift 2
+            ;;
+        --help|-h)
+            sed -n '2,/^$/{ /^$/!p }' "$0"
+            exit 0
+            ;;
+        *)
+            echo "ERROR: Unknown option: $1" >&2
+            echo "Usage: $0 [--overwrite] [--source <url>]" >&2
+            exit 1
+            ;;
+    esac
+done
+
+# ── Helper: install a single factory preset file ────────────────────────────
+
+install_preset() {
+    local src="$1"
+    local dest_dir="$2"
+    local overwrite="$3"
+
+    # Derive target path: presets/factory/bank_0/preset_1.json → bank_0/preset_1.json
+    local rel_path="${src#$FACTORY_SOURCE/}"
+    local dest="$dest_dir/$rel_path"
+
+    if [[ -f "$dest" && "$overwrite" != "true" ]]; then
+        echo "  SKIP  $(basename "$(dirname "$dest")")/$(basename "$dest") (exists)"
+        return 1
+    fi
+
+    mkdir -p "$(dirname "$dest")"
+    cp "$src" "$dest"
+    echo "  INSTALL  $(basename "$(dirname "$dest")")/$(basename "$dest")"
+    return 0
+}
+
+# ── Main ────────────────────────────────────────────────────────────────────
+
+echo "Pi Multi-FX Pedal — Factory Preset Installer"
+echo "============================================="
+echo ""
+
+# Option 1: Install from bundled local presets
+if [[ -d "$FACTORY_SOURCE" ]]; then
+    echo "Found bundled factory presets at: $FACTORY_SOURCE"
+    echo "Installing to: $PRESET_DIR"
+    echo ""
+
+    count=0
+    skipped=0
+    while IFS= read -r -d '' preset_file; do
+        if install_preset "$preset_file" "$PRESET_DIR" "$OVERWRITE"; then
+            count=$((count + 1))
+        else
+            skipped=$((skipped + 1))
+        fi
+    done < <(find "$FACTORY_SOURCE" -name 'preset_*.json' -print0)
+
+    echo ""
+    echo "Done: $count installed, $skipped skipped"
+    exit 0
+
+# Option 2: Download from fallback URL
+elif [[ -n "$FALLBACK_URL" ]]; then
+    echo "Local factory presets not found at: $FACTORY_SOURCE"
+    echo "Downloading from: $FALLBACK_URL"
+    echo ""
+
+    TMP_ZIP=$(mktemp /tmp/pedal-presets-XXXXXX.zip)
+    trap 'rm -f "$TMP_ZIP"' EXIT
+
+    if command -v curl &>/dev/null; then
+        curl -fsSL "$FALLBACK_URL" -o "$TMP_ZIP"
+    elif command -v wget &>/dev/null; then
+        wget -q "$FALLBACK_URL" -O "$TMP_ZIP"
+    else
+        echo "ERROR: Neither curl nor wget found" >&2
+        exit 1
+    fi
+
+    TMP_DIR=$(mktemp -d /tmp/pedal-presets-XXXXXX)
+    trap 'rm -rf "$TMP_DIR" "$TMP_ZIP"' EXIT
+    unzip -q "$TMP_ZIP" -d "$TMP_DIR"
+
+    count=0
+    while IFS= read -r -d '' preset_file; do
+        rel_path="${preset_file#$TMP_DIR/}"
+        dest="$PRESET_DIR/$rel_path"
+        if [[ -f "$dest" && "$OVERWRITE" != "true" ]]; then
+            echo "  SKIP  $(basename "$(dirname "$dest")")/$(basename "$dest")"
+            continue
+        fi
+        mkdir -p "$(dirname "$dest")"
+        cp "$preset_file" "$dest"
+        count=$((count + 1))
+        echo "  INSTALL  $(basename "$(dirname "$dest")")/$(basename "$dest")"
+    done < <(find "$TMP_DIR" -name 'preset_*.json' -print0)
+
+    echo ""
+    echo "Done: $count installed from remote source"
+    exit 0
+
+else
+    echo "ERROR: No factory presets found at '$FACTORY_SOURCE'"
+    echo ""
+    echo "The project ships factory presets in presets/factory/."
+    echo "If you're running from a cloned repo, run from the project root:"
+    echo "  ./scripts/download_presets.sh"
+    echo ""
+    echo "Alternatively, pass --source <url> to download a preset archive."
+    exit 1
+fi