fix(cli): pass u64 limit/offset to regenerated client

[nicoloboschi]

Problem

cargo build for the Rust CLI fails on main, breaking the test-rust-cli and test-doc-examples (cli) CI jobs:

error[E0308]: arguments to this method are incorrect
  --> src/api.rs:426
note: expected `Option<u64>`, found `Option<i64>`

The generated hindsight-client was regenerated with limit/offset typed as Option<u64> (the OpenAPI spec marks them as unsigned, minimum: 0), but the hand-written api.rs wrappers still passed Option<i64>.

Fix

Cast limit/offset to u64 at each affected call site — list_documents, list_memories, list_entities, get_graph, list_tags — matching the as i64→as u64 pattern already used for list_documents. No wrapper signatures or callers change.

Verification

• cargo build — clean
• cargo test — 57 + 24 + 11 + 7 tests pass
• cargo fmt --check — clean