Release v3.0.0-pre6

What's Changed

• Make keyword de-clutter and bilingual synonyms coexist by @bmachek in #224
• fix(plugin): apply top-level keyword when hierarchy is disabled by @bmachek in #227
• fix(server): honor custom prompt and date_time on the index routes by @bmachek in #228
• perf(server): re-enable KleidiAI kernels, ~3x faster indexing by @bmachek in #231

Full Changelog: v3.0.0-pre4...v3.0.0-pre6