Fix R8: compact JSON for the large media-items store

writeJsonAtomic always pretty-printed (JSON.stringify(value, null, 2)), which
needlessly inflates size and write time for the media-items store (up to
MAX_ITEMS=20000 rows). Added an optional `pretty` flag (default true, so
history/sources/templates/errorlog stay hand-inspectable) threaded through
createJsonStore, and set it false for media-items.json.

typecheck + 242 tests + eslint green.

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

CODE-AUDIT.md

@@ -1350,7 +1350,7 @@ cosmetics. `R` IDs.
 - [ ] **R7 — `safeStorage` unavailable ⇒ secrets silently stored as plaintext.** `encryptSecret` falls back
   to plaintext when DPAPI/safeStorage isn't available, with no indication — compounds H7 (cookies) and the
   backup-cleartext issue (M22). **Fix:** warn (or refuse to store) when encryption is unavailable.
-- [ ] **R8 — Pretty-printed JSON for large stores.** `JSON.stringify(value, null, 2)` inflates size/write
+- [x] **R8 — Pretty-printed JSON for large stores.** `JSON.stringify(value, null, 2)` inflates size/write
   time for the potentially-20k-item media store (ties R3). **Fix:** compact JSON for the large stores.
 - [ ] **R9 — Clock-skew sensitivity.** `shouldAutoCheckYtdlp` and the scheduled-download promoter compare
   `Date.now()`; a backward system-clock correction can skip or double-fire a check/schedule. Minor; note for awareness.

src/main/jsonStore.ts

@@ -7,13 +7,13 @@ import { readFileSync, writeFileSync, renameSync, existsSync, copyFileSync } fro
  * error log, templates, sources, media-items). Replaces the per-module
  * read/parse/write copies (SIMP1) and fixes three data-safety blockers:
  *
- *  - R1 — atomic writes: write a temp file then `rename` over the target, so a
+ *  - R1 -- atomic writes: write a temp file then `rename` over the target, so a
  *    crash / power-cut mid-write can never truncate the real file. (`electron-store`,
  *    used for settings, is already atomic; these stores were not.)
- *  - R2 — corruption is no longer silent data loss: on a parse error the bad file
+ *  - R2 -- corruption is no longer silent data loss: on a parse error the bad file
  *    is copied aside (`<file>.corrupt-<ts>`) before we fall back to empty, so a
  *    single bad byte can't wipe the user's history/sources from their perspective.
- *  - R3 — an in-memory cache + debounced batched writes: the previous code
+ *  - R3 -- an in-memory cache + debounced batched writes: the previous code
  *    re-read + re-parsed the entire (multi-MB) file and rewrote it synchronously
  *    on *every* download completion (≈O(n²) over a large channel, blocking the
  *    main thread). Reads now hit the cache; writes coalesce into one atomic flush.
@@ -44,22 +44,24 @@ export function readJsonArraySafe<T>(path: string, isValid: (o: unknown) => o is
     try {
       copyFileSync(path, `${path}.corrupt-${Date.now()}`)
     } catch {
-      /* best-effort — if we can't back it up, still don't crash the read */
+      /* best-effort -- if we can't back it up, still don't crash the read */
     }
     return []
   }
 }
 
 /**
- * Atomically write `value` as pretty JSON to `path`: serialise to `<path>.tmp`,
+ * Atomically write `value` as JSON to `path`: serialise to `<path>.tmp`, then
- * then `rename` it over the target (an atomic operation on the same volume), so a
+ * `rename` it over the target (an atomic operation on the same volume), so a
- * crash mid-write leaves either the old file or the new one — never a truncated
+ * crash mid-write leaves either the old file or the new one -- never a truncated
- * one (R1). Best-effort: a read-only data dir just means nothing is persisted.
+ * one (R1). `pretty` indents for human-readable files; pass false for large
+ * machine-only stores to avoid inflating size/write time (R8). Best-effort: a
+ * read-only data dir just means nothing is persisted.
  */
-export function writeJsonAtomic(path: string, value: unknown): void {
+export function writeJsonAtomic(path: string, value: unknown, pretty = true): void {
   const tmp = `${path}.tmp`
   try {
-    writeFileSync(tmp, JSON.stringify(value, null, 2))
+    writeFileSync(tmp, pretty ? JSON.stringify(value, null, 2) : JSON.stringify(value))
     renameSync(tmp, path)
   } catch {
     /* best-effort; e.g. a read-only data dir */
@@ -86,7 +88,10 @@ const registry: JsonStore<unknown>[] = []
 export function createJsonStore<T>(
   filename: string,
   isValid: (o: unknown) => o is T,
-  cap: number
+  cap: number,
+  // Pretty-print by default (small, hand-inspectable files); pass false for a
+  // large machine-only store to keep writes compact (R8).
+  pretty = true
 ): JsonStore<T> {
   let cache: T[] | null = null
   let timer: ReturnType<typeof setTimeout> | null = null
@@ -106,7 +111,7 @@ export function createJsonStore<T>(
     }
     if (!dirty) return
     dirty = false
-    writeJsonAtomic(filePath(), cache ?? [])
+    writeJsonAtomic(filePath(), cache ?? [], pretty)
   }
 
   function write(items: T[]): T[] {
@@ -124,7 +129,7 @@ export function createJsonStore<T>(
   return store
 }
 
-/** Synchronously flush every store's pending write — call on app quit. */
+/** Synchronously flush every store's pending write -- call on app quit. */
 export function flushAllStores(): void {
   for (const s of registry) s.flush()
 }

src/main/sources.ts

@@ -27,7 +27,9 @@ const MAX_ITEMS = 20000
 // rewrite the whole (≤MAX_ITEMS) file on every completion; now reads hit the
 // cache and writes are batched. Sources are few, so that store is uncapped.
 const sourcesStore = createJsonStore('sources.json', isValidSource, Infinity)
-const itemsStore = createJsonStore('media-items.json', isValidMediaItem, MAX_ITEMS)
+// Compact (not pretty) -- this store can hold up to MAX_ITEMS rows; indentation
+// would needlessly inflate its size and write time (R8).
+const itemsStore = createJsonStore('media-items.json', isValidMediaItem, MAX_ITEMS, false)
 
 // --- Sources ----------------------------------------------------------------