feat(config): real config reset/repair + migration framework (drop manual-delete) (#38)

Eliminates the fragile "delete the config folder before upgrading" tester
instruction, which was wrong-by-OS because the userData folder name was
derived inconsistently per platform (fee[dB]ack on macOS, slopsmith-desktop
on Linux/Windows).

A. Deterministic paths + migration framework
- Pin the userData name on every OS via app.setName('feedback-desktop') +
  build.extraMetadata.name; brand (productName 'fee[dB]ack') unchanged.
- One-time userData migration copies a legacy folder into the new one so
  upgraded users don't start fresh (atomic copy-then-rename, fail-soft).
  Runs before the single-instance lock / crashReporter, which would otherwise
  create userData and defeat the "new dir doesn't exist" gate.
- config-migrations.ts: versioned, ordered, idempotent, fail-soft migration
  runner stamped in CONFIG_DIR/config_version.json; logs the active CONFIG_DIR
  at startup (closes the Linux ~/.local/share/slopsmith shared-config gap).

B. In-app "Reset / repair configuration" (Settings panel)
- Granular options: reset app settings & caches, clear plugin state & cached
  Python deps, and full reset with default-OFF opt-ins for installed plugins /
  song library / ML caches.
- config-paths.ts is the single source of truth for per-OS path enumeration;
  the song library, installed plugins and ML caches are structurally confined
  to optInExtras and never wiped by the safe/full categories.
- Reset stops the backend, deletes immediate paths, includes SQLite WAL/SHM
  sidecars + the migration stamp on full reset, and defers Chromium/Crashpad
  state to next launch (consumed before any window reopens it). ML caches honor
  TORCH_HOME/HF_HOME. Empty selection is a no-op (backend left running).
- SECURITY: destructive resets require a native main-process confirmation
  dialog — the renderer bridge is reachable by plugin scripts, so a
  renderer-only confirm is not a sufficient gate.

Tests: node:test suites for path enumeration (per-OS + library/plugins
preserved), migration idempotency/fail-soft, reset delete pipeline guarantees,
userData migration, and deferred-deletion schedule/consume. `npm test` green
(adds a test script). codex review --base origin/main clean.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package.json

@@ -10,6 +10,7 @@
   "main": "dist/main/main.js",
   "scripts": {
     "typecheck": "tsc --noEmit",
+    "test": "node --test \"tests/*.test.js\"",
     "build:ts": "tsc && node -e \"const fs=require('fs'),path=require('path');fs.copyFileSync('src/main/splash.html','dist/main/splash.html');fs.copyFileSync('src/main/spinner.json','dist/main/spinner.json');fs.copyFileSync('node_modules/lottie-web/build/player/lottie.min.js','dist/main/lottie.min.js');const dst='dist/main/images';if(fs.existsSync(dst))fs.rmSync(dst,{recursive:true});fs.mkdirSync(dst,{recursive:true});fs.readdirSync('src/main/images',{withFileTypes:true}).filter(d=>d.isFile()&&d.name.endsWith('.webp')).forEach(d=>fs.copyFileSync(path.join('src/main/images',d.name),path.join(dst,d.name)))\"",
     "build:audio": "bash scripts/build-audio.sh Release",
     "build:audio:debug": "bash scripts/build-audio.sh Debug",
@@ -32,6 +33,9 @@
     "appId": "com.byron.slopsmith-desktop",
     "productName": "fee[dB]ack",
     "executableName": "feedback",
+    "extraMetadata": {
+      "name": "feedback-desktop"
+    },
     "artifactName": "feedback-${version}-${arch}.${ext}",
     "directories": {
       "output": "release"