Release v4.6.7-beta.2

What's Changed

• perf(selector): reduce large channel routing allocations (c0d93b30)
• fix(proxy): classify interrupted streams as 599 (9364cede)
• fix(proxy): preserve 499 and 598 stream error semantics (38e01749)
• refactor(selector): tighten slice ownership in routing hot path (1bf84c8a)

Full Changelog: v4.6.7-beta.1...v4.6.7-beta.2