Harden audit findings: correctness, type-safety, Windows conventions & polish

Audit-pass over CODE-AUDIT.md (~48 items closed this pass; all verified —
typecheck + 234 tests + eslint + prettier green).

Correctness / bugs:
- B3: match the release checksum to the asset's filename line (no wrong-hash verify)
- B4: newline-safe metadata probe (one --print with a unit-separator delimiter)
- B5 / L88: guard the meta event against canceled items; progress no longer promotes
  a queued item outside pump()
- B7: cookie-login promise always resolves (handles destroy-without-close)
- L146: trim parser rejects >2 colon-group times; M36: Library selection counts only
  actionable rows
- L11 / L50 / L156 / L57 / L159 / L15 / L3: live queue count, empty-cookie message,
  schedule picker min, dead-code/comment cleanup

Type safety:
- Enable noUncheckedIndexedAccess + noFallthroughCasesInSwitch (15 real edge cases fixed)

Resilience / Windows / metadata:
- R5: settings write failure handled (no unhandled IPC rejection; reconciles to truth)
- W1 / W5 / W6: min window size, seeded folder picker, parented sign-in window;
  L147 dead macOS branches removed
- CL1: shared stdout markers; package/builder metadata (license, homepage, repository,
  copyright, tsbuildinfo glob)

Copy / docs / tests:
- M37 / SR9 dev-jargon cleanup in hints; M8 / M25 / M26 / L66 / L80 / L81 reconciled
- New unit tests for L35 (isValidMediaItem) and L36 (compareVersions)

This commit also checkpoints the previously-uncommitted feat/tray-background-clipboard
work it builds on: background running + auto-download, library clipboard detection,
tray, binary management & library scale, credential encryption at rest, the shared
jsonStore and ui/ primitives, and the eslint/prettier tooling.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main/templates.ts

@@ -1,38 +1,21 @@
-import { app } from 'electron'
-import { join } from 'path'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
 import type { CommandTemplate } from '@shared/ipc'
 import { isTemplateLike } from './validation'
+import { createJsonStore } from './jsonStore'
 
-// Plain JSON in userData, same shape as history.ts.
+// Plain JSON in userData, same shape as history.ts. Atomic writes / corruption
+// backup / caching come from the shared jsonStore (R1–R3).
 const MAX_TEMPLATES = 100
 
-function templatesFile(): string {
-  return join(app.getPath('userData'), 'templates.json')
-}
-
 // A persisted template entry must at least be an object carrying an id (see
 // isTemplateLike in validation.ts); everything else is coerced by sanitize().
 // Drop anything that isn't, so a hand-edited templates.json can't inject
 // malformed entries. (audit S5)
-export function listTemplates(): CommandTemplate[] {
-  try {
-    if (!existsSync(templatesFile())) return []
-    const data = JSON.parse(readFileSync(templatesFile(), 'utf8'))
-    // Validate shape, then normalise each surviving entry through sanitize() so
-    // name/args are always well-formed strings regardless of what was on disk.
-    return Array.isArray(data) ? data.filter(isTemplateLike).map(sanitize) : []
-  } catch {
-    return []
-  }
-}
+const store = createJsonStore('templates.json', isTemplateLike, MAX_TEMPLATES)
 
-function save(templates: CommandTemplate[]): void {
-  try {
-    writeFileSync(templatesFile(), JSON.stringify(templates.slice(0, MAX_TEMPLATES), null, 2))
-  } catch {
-    /* best-effort; a read-only data dir just means no persisted templates */
-  }
+export function listTemplates(): CommandTemplate[] {
+  // Normalise each surviving entry through sanitize() so name/args are always
+  // well-formed strings regardless of what was on disk.
+  return store.read().map(sanitize)
 }
 
 function sanitize(t: CommandTemplate): CommandTemplate {
@@ -49,20 +32,14 @@ function sanitize(t: CommandTemplate): CommandTemplate {
 /** Add a new template, or update an existing one (matched by id). */
 export function saveTemplate(template: CommandTemplate): CommandTemplate[] {
   const clean = sanitize(template)
-  const templates = [clean, ...listTemplates().filter((t) => t.id !== clean.id)]
-  save(templates)
-  return templates
+  return store.write([clean, ...listTemplates().filter((t) => t.id !== clean.id)])
 }
 
 export function removeTemplate(id: string): CommandTemplate[] {
-  const templates = listTemplates().filter((t) => t.id !== id)
-  save(templates)
-  return templates
+  return store.write(listTemplates().filter((t) => t.id !== id))
 }
 
 /** Replace the entire template list (backup restore) rather than merge-by-id. */
 export function replaceTemplates(templates: CommandTemplate[]): CommandTemplate[] {
-  const clean = templates.map(sanitize)
-  save(clean)
-  return clean
+  return store.write(templates.map(sanitize))
 }