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/history.ts

@@ -1,59 +1,39 @@
-import { app } from 'electron'
-import { join } from 'path'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
 import type { HistoryEntry } from '@shared/ipc'
 import { isValidHistoryEntry } from './validation'
+import { createJsonStore } from './jsonStore'
 
 // Plain JSON in userData (portable build redirects userData next to the exe).
-// Kept simple per the build plan; can migrate to better-sqlite3 later.
+// Kept simple per the build plan; can migrate to better-sqlite3 later. Atomic
+// writes, corruption backup, and caching come from the shared jsonStore (R1–R3).
 const MAX_ENTRIES = 500
 
-function historyFile(): string {
-  return join(app.getPath('userData'), 'history.json')
-}
+// Per-entry validation (isValidHistoryEntry) so a hand-edited or corrupted
+// history.json can't feed the UI (or openPath) entries with the wrong shape —
+// invalid rows are dropped rather than trusted. (audit S5)
+const store = createJsonStore('history.json', isValidHistoryEntry, MAX_ENTRIES)
 
-// Per-entry validation (isValidHistoryEntry, in validation.ts) so a hand-edited
-// or corrupted history.json can't feed the UI (or openPath) entries with the
-// wrong shape — invalid rows are dropped rather than trusted. (audit S5)
 export function listHistory(): HistoryEntry[] {
-  try {
-    if (!existsSync(historyFile())) return []
-    const data = JSON.parse(readFileSync(historyFile(), 'utf8'))
-    return Array.isArray(data) ? data.filter(isValidHistoryEntry) : []
-  } catch {
-    return []
-  }
-}
-
-function save(entries: HistoryEntry[]): void {
-  try {
-    writeFileSync(historyFile(), JSON.stringify(entries.slice(0, MAX_ENTRIES), null, 2))
-  } catch {
-    /* best-effort; a read-only data dir just means no persisted history */
-  }
+  return store.read()
 }
 
 export function addHistory(entry: HistoryEntry): HistoryEntry[] {
-  // De-dupe by id (a retry of the same item replaces its prior entry).
-  const entries = [entry, ...listHistory().filter((e) => e.id !== entry.id)]
-  save(entries)
-  return entries
+  // De-dupe by id AND url (M35): a History re-download re-queues via addFromUrl,
+  // which mints a NEW id, so id-only de-dup would let the same video accumulate a
+  // fresh row on every re-download. Dropping any prior entry with the same url
+  // keeps one row per video, refreshed to the top.
+  const prior = listHistory().filter((e) => e.id !== entry.id && e.url !== entry.url)
+  return store.write([entry, ...prior])
 }
 
 export function removeHistory(id: string): HistoryEntry[] {
-  const entries = listHistory().filter((e) => e.id !== id)
-  save(entries)
-  return entries
+  return store.write(listHistory().filter((e) => e.id !== id))
 }
 
 export function removeManyHistory(ids: string[]): HistoryEntry[] {
   const remove = new Set(ids)
-  const entries = listHistory().filter((e) => !remove.has(e.id))
-  save(entries)
-  return entries
+  return store.write(listHistory().filter((e) => !remove.has(e.id)))
 }
 
 export function clearHistory(): HistoryEntry[] {
-  save([])
-  return []
+  return store.write([])
 }