* chore(release): prepare 0.2.50

Move reconciled Unreleased notes into the dated release and update package metadata. Existing README, usage, AI Insights and cost guides already describe the release behavior; TODO blockers remain unchanged. Verified make check, make package and tagged changelog extraction. Local KDE-dependent skips and partial type checks require full CI coverage.

* docs(changelog): restore conjunction in cost history entry

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Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>