fix(ai): align fixed broker with loaded plans

[first-assist]

Summary

• make optional fixed-broker wrapper fields genuinely optional
• describe the closed scalar-path translation from the loaded planning schema
• verify the minimal schema-aligned wrapper through the core and provider projections

Safety

The authoritative compiler, loaded-reference binding, authorization, expiry, finite-path validation, and result bounds remain unchanged. The broker still rejects unknown wrapper fields and never accepts raw query text.

Release

• bumps graphql-orm-ai from 0.96.1 to 0.96.2
• refreshes both lockfiles with internal version-only changes
• updates release and migration documentation

Documentation impact

• Documentation updated
• No documentation impact

Verification

• full package tests
• focused fixed-broker tests
• warnings-denied Clippy
• warnings-denied Rustdoc
• formatting and diff checks
• documentation, release, dependency, package-policy, manifest, and SemVer gates
• committed-diff neutrality scan