Release 25.4.4

Fixes TypeScript Gemini context caching to preserve all system instructions, and adds abort-signal and UTF-8 decoder fallback regression tests. Generated-language parity remains tracked in the AxIR backlog. Existing Gemini caches need expiry or recreation to receive the corrected instructions.

What's Changed

• fix(gemini): preserve every system message in context caches by @YizukiAme in #851
• test: cover mergeAbortSignals fallback cleanup by @pacocartones in #859
• test: cover UTF-8 buffering and flush in decoder polyfill by @pacocartones in #860
• chore: release v25.4.4 by @dosco in #861

Full Changelog: 25.4.3...25.4.4