fix(code-index): calls through function-local use are dropped as complete

[ScriptedAlchemy]

Problem

A qualified Rust call that goes through a use declared inside a function body or block does not bind, and tracedecay_callers still reports coverage.completeness = complete for the target. The caller is silently missing.

Reproduction

tokio 1.53.1 (tag tokio-1.53.1), indexed with the shipped CLI on an isolated profile. tokio/src/runtime/context/current.rs::with_current has seven call sites of the form context::with_current(...) in tokio/src. tracedecay_callers (depth 1) returns 5 with complete. The two missing callers both import context inside the function:

• tokio/src/task/spawn.rs:188 spawn_inner: use crate::runtime::{context, task}; at the top of the function body, then context::with_current(...) at line 211.
• tokio/src/runtime/time_alt/timer.rs:72: use crate::runtime::context; inside a #[cfg(feature = "rt")] { ... } block, then context::with_current(...) at line 78.

The five resolved callers import context at module scope.

Expected: both calls bind to with_current. If function-scoped imports are not modeled, the answer should be partial with a typed omission rather than complete.