fix(sdk): close conformance gaps in the agent, directory and service

[zhoodar]

Summary

• Complete the Agent, Directory, and Service conformance audit with regression coverage.
• Pin validated network destinations, constrain supporting-document redirects and response sizes, and isolate shared-cache authentication contexts.
• Preserve schema reference graphs and redirect bases; correct normalization, version compatibility, refinement comparisons, and depth limits.
• Correct retrieval defaults, search limits and continuations, conditional responses, collection hierarchy validation, and Directory metadata retention.
• Update integration documentation and exercise protocol-version vectors without changing odp-specs.

Verification

• make verify and make conformance on stable Rust and Rust 1.85.0.
• RUSTUP_TOOLCHAIN=1.85.0 make consumer-smoke.
• ODP_INTEROP_PORT=41987 make interoperability against the Node example Service.
• cargo llvm-cov --workspace --all-features --locked --summary-only.
• git diff --check.

The shared conformance adapter still reports unsupported vector categories as skipped; these are not counted as passing. SDK-specific tests additionally cover network, cache, catalog, and failure paths.