Rust Crate v1.12.0

Added

• (unstable-v2) patch upsert _meta by top-level key (#2372)
• (unstable) add client system prompt schema (#2361)
• (rust) implement Eq for content blocks (#2352)

Fixed

• (unstable) remove next edit suggestions (#2266)
• (schema) align v2 experimental feature compatibility (#2397)

Other

• (unstable-v2) define foreground state transitions (#2411)
• (v2) clarify replay IDs and unsupported cursors (#2398)
• (v2) align normative cancellation requirements (#2390)
• (unstable-v2) clarify prompt insertion contract (#2392)
• (unstable-v2) clarify foreground work lifecycle (#2387)
• (v2) clarify prompt cancellation when closing sessions (#2385)
• (schema) specify how git_patch writes paths (#2362)
• (unstable) clarify that a forked session is active (#2359)
• (schema) list full v2 session baseline on AgentCapabilities.session (#2358)
• (schema) clarify v2 foreground work can start without a prompt (#2357)