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/errorlog.ts

@@ -1,45 +1,24 @@
-import { app } from 'electron'
-import { join } from 'path'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
 import type { ErrorLogEntry } from '@shared/ipc'
 import { isValidErrorLogEntry } from './validation'
+import { createJsonStore } from './jsonStore'
 
 // Plain JSON in userData, same shape as history.ts. Persisted so a failure
-// report survives the queue item being cleared (Seal's "debug report").
+// report survives the queue item being cleared (Seal's "debug report"). Atomic
+// writes / corruption backup / caching come from the shared jsonStore (R1–R3).
 const MAX_ENTRIES = 200
 
-function errorLogFile(): string {
-  return join(app.getPath('userData'), 'errorlog.json')
-}
+// Per-entry validation (isValidErrorLogEntry) so a hand-edited or corrupted
+// errorlog.json can't feed the UI entries with the wrong shape. (audit S5)
+const store = createJsonStore('errorlog.json', isValidErrorLogEntry, MAX_ENTRIES)
 
-// Per-entry validation (isValidErrorLogEntry, in validation.ts) so a hand-edited
-// or corrupted errorlog.json can't feed the UI entries with the wrong shape —
-// invalid rows are dropped. (audit S5)
 export function listErrorLog(): ErrorLogEntry[] {
-  try {
-    if (!existsSync(errorLogFile())) return []
-    const data = JSON.parse(readFileSync(errorLogFile(), 'utf8'))
-    return Array.isArray(data) ? data.filter(isValidErrorLogEntry) : []
-  } catch {
-    return []
-  }
-}
-
-function save(entries: ErrorLogEntry[]): void {
-  try {
-    writeFileSync(errorLogFile(), JSON.stringify(entries.slice(0, MAX_ENTRIES), null, 2))
-  } catch {
-    /* best-effort; a read-only data dir just means no persisted error log */
-  }
+  return store.read()
 }
 
 export function addErrorLog(entry: ErrorLogEntry): ErrorLogEntry[] {
-  const entries = [entry, ...listErrorLog()]
-  save(entries)
-  return entries
+  return store.write([entry, ...listErrorLog()])
 }
 
 export function clearErrorLog(): ErrorLogEntry[] {
-  save([])
-  return []
+  return store.write([])
 }