Add build and run scripts; drop the broken Avalonia.Diagnostics reference

A wrapper around `dotnet build` earns nothing, so build.ps1/build.sh are the
full local gate instead — tool restore, package restore, format check, build,
test — in the order that fails cheapest first, with a non-zero exit on failure.
run.ps1/run.sh default to Debug and pass extra arguments through to the app.
Both flavours ship because the Desktop head targets Windows, Linux and macOS.

Writing them immediately paid for itself: the very first run failed restore on
Avalonia.Diagnostics 12.1.1, which does not exist — the package stops at 11.3.x
because Avalonia 12 moved the inspector into a separate tool with its own
installation. The reference had survived because it sat behind
Condition="'$(Configuration)' == 'Debug'", and `dotnet restore` evaluates with
the default configuration while every build so far had passed -c Release. So
`dotnet build -c Release` worked and a bare `dotnet restore` did not.

Reference removed rather than replaced: AvaloniaUI.DiagnosticsSupport pulls in a
separately installed tool, which is not a dependency to add to a skeleton without
asking. README and CLAUDE.md no longer promise F12, and both traps are written
down where the next person will hit them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

run.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+# Запускает desktop-приложение.
+#
+# По умолчанию Debug: быстрее собирается и даёт осмысленные стеки. Инспектора в Avalonia 12
+# из коробки нет — см. README.
+#
+#   ./run.sh                        Debug
+#   ./run.sh -c Release --no-build  запустить уже собранное
+#   ./run.sh -- --какой-то-аргумент передать аргументы приложению
+
+set -euo pipefail
+cd "$(dirname "$0")"
+
+CONFIGURATION=Debug
+NO_BUILD=0
+APP_ARGS=()
+
+while [ $# -gt 0 ]; do
+    case "$1" in
+        -c|--configuration) CONFIGURATION="$2"; shift 2 ;;
+        --no-build)         NO_BUILD=1; shift ;;
+        -h|--help)          sed -n '2,9p' "$0"; exit 0 ;;
+        --)                 shift; APP_ARGS=("$@"); break ;;
+        *) echo "Неизвестный аргумент: $1 (аргументы приложения — после --)" >&2; exit 2 ;;
+    esac
+done
+
+ARGS=(run --project src/AvParser.Desktop -c "$CONFIGURATION")
+[ "$NO_BUILD" -eq 1 ] && ARGS+=(--no-build)
+[ ${#APP_ARGS[@]} -gt 0 ] && ARGS+=(-- "${APP_ARGS[@]}")
+
+printf '\033[36m==> dotnet %s\033[0m\n' "${ARGS[*]}"
+exec dotnet "${ARGS[@]}"