Stop no longer flushes the queue: a user-initiated Stop now skips exactly the
auto-drain triggered by its resulting idle (one-shot guard). The queue stays
intact, the next message the user sends fires immediately (priority, not
queued — even with items waiting), and the queue resumes FIFO on the next idle
after that turn. Queue enqueue/drain/edit mechanics are otherwise unchanged.
Also removes the Buy-Me-a-Coffee / donation section from README (zh/en).
Bumps desktop app to 0.5.3 with release notes.
Tested: desktop tsc --noEmit; Vitest chatStore 94 + pages/ActiveSession 43
passed (incl. stop-no-flush / priority-message / queue-resume case); Windows
x64 NSIS package + package-smoke PASS.
Scope-risk: narrow
Confidence: high
