Release v4.9.1-beta.12

What's Changed

• refactor(oauthcost): scope usage rollback to individual windows (83bbea8b)
• refactor(wire): drop map as the JSON intermediate representation (53ea5eac)
• fix(responses): restore the upstream JSON validity gate in the SSE bridge (501f27e1)
• fix Zed null field removal treating literal keys as sjson paths (35b805d4)
• converge Antigravity schema aliases onto the canonical field (abac986a)
• cap all JSON walkers at depth 20, index wide objects, keep raw keys (39ee4df5)
• fold the Antigravity generation_config parent into generationConfig (f6594816)
• fix(wire): align response decoding with gjson duplicate-member semantics (58f3220b)
• fix(usage): funnel usage numeric conversion through a single guarded entry (08b19651)
• fix(anthropic): stop requiring cch to recognize native Claude Code requests (70370bb0)
• fix(anthropic): align native Claude Code identity and UA checks with upstream (0df63d56)
• refactor(anthropic): reduce native Claude Code detection to upstream's four signals (a82a4d29)
• fix(anthropic): 把原生 Claude Code 判据收敛成三个请求头 (032f4e80)
• fix(usage): 流式 usage 的零值占位不再覆盖有效累计快照 (e51106b4)
• fix(antigravity): Claude 目标响应的 usage 减去缓存命中的输入 (f490cf2e)

Full Changelog: v4.9.1-beta.11...v4.9.1-beta.12