Universal Spell Check v0.1.7

fix: harden clipboard operations against transient lock contention

Recent prod failures in Slack, Codex, and Chrome all collapsed to the same root cause: the clipboard path assumed every Clipboard.* call would succeed immediately. Under transient Windows clipboard contention that turned a recoverable lock into a hard capture or paste failure.\n\nThis change adds bounded retry around the clipboard operations that matter on the hot path: backup, sentinel write, capture polling reads, corrected-text publish, and restore. The behavior stays clipboard-first with the same Ctrl+V replacement model, but transient ExternalException cases now wait briefly and succeed instead of aborting the run.\n\nDocs were updated to match the actual dev app version stamping behavior in logs so channel and build attribution stays clear during prod/dev verification.