Resolves conflicts with the independently developed skill-market/SkillCenter
feature that landed on main after this branch diverged. Keeps the market
rewrite as the sole implementation:
- Removes the parallel skill-market stack (server api/skill-market.ts,
services/skillMarket/, SkillCenter.tsx, skillMarketStore.ts, related tests
and i18n keys) in favor of the market implementation from this branch.
- Restores the Settings > Skills tab (and its redirect-free behavior) that
the removed implementation had folded into a top-level Skill Center tab,
keeping local skill browsing on SkillDetailView alongside the online market.
- Adapts tests and callers (TabBar, ContentRouter, PluginDetail,
LocalSlashCommandPanel, persistence migrations) from skill-center/
SKILL_CENTER_TAB_ID naming to market/MARKET_TAB_ID.
25ebc05a42