fix: hardening round from code review (4 P1 + 15 P2)

P1:
- settingsStore: back up an unparseable settings.json to .bak before
  falling back to defaults, so the next mutation can no longer silently
  wipe custom themes/highlight rules
- ptyDispatcher: fan out per-session data/exit handlers (Set instead of
  a single slot) so SSH split panes stop stealing each other's stream
- FilePanel: monotonic refresh token keeps stale listings from painting
  over a newer navigation; upload finish no longer yanks the panel back
- settings.css: active settings-tab label derives from --chrome-fg so it
  stays visible on the shipped light themes

P2 (main/renderer):
- paste guard: a paste ending in a newline always confirms
- Workspace: closing an SSH pane no longer seeds the local cwd with a
  remote path
- tray: skip close-dialog continuation on a destroyed window
- commands: close zombie 'in-progress' session logs at hydrate
- zmodem: clear the stale offer timer before arming a new one
- connectionsStore: coerce/validate renderer input before persisting
- sftp: OperationError marker class keeps translated errors out of the
  transport-retry classifier
- CommandsPanel: surface save failures inside the dialog
- ConnectionSidebar: drop a tautological tooltip condition

P2 (i18n/tooling/tests):
- localize the 16 ANSI color labels and the highlight sample text
  (21 new keys across zh-CN/zh-TW/en/ja)
- sync-changelog: keep ### subheadings, normalize CRLF notes
- release.cjs: GitHub release reuse-by-tag (idempotent re-runs); fail
  loudly on a failed Gitea asset listing
- commands-store test: absent historyEnabled now truly tests absence

src/main/zmodem.ts

@@ -342,6 +342,11 @@ export function attachZmodem(sessionId: string, deps: ZmodemDeps): void {
         } catch {
           // never crash the event loop
         }
+        // Clear any previous offer timer first: a re-detect while an earlier
+        // offer is still pending overwrites engine.offerTimer, and the orphaned
+        // timer would fire at its original deadline and abort a legitimate
+        // pending offer ahead of its own timeout.
+        if (engine.offerTimer) clearTimeout(engine.offerTimer)
         engine.offerTimer = setTimeout(() => {
           if (engine.detection && !engine.confirmed) {
             abortWithoutSession(engine, t('main.zmodem.offerTimedOut'))