ForegroundPressure had two definitions with byte-identical pressure computation: one in ecstore data-movement backpressure and one in the heal manager queue. That duplication is a violation of the ARCHITECTURE.md invariant that each type has exactly one definition, and it means any future change to the utilization math has to land twice.
Add the canonical `ForegroundPressure` and a `foreground_pressure(snapshot, read_threshold_pct, write_threshold_pct)` function to `crates/concurrency/src/workload.rs`, which already owns `WorkloadClass`, `AdmissionState`, and the admission snapshot contract. Both existing consumers already depend on `rustfs-concurrency`, so no crate edge is added.
The filter_map pipeline is transferred verbatim, preserving all five boundary behaviors (zero threshold, zero limit, missing entry, missing active count, and the `Saturated` full-utilization special case), the mul-before-div percentage normalization, the `>=` threshold comparison, and the read-then-write ordering that makes `max_by_key` break utilization ties toward the write class. The enable switch is deliberately left out: ecstore gates on `config.enabled` while heal gates on `mainline_throttle_enable` plus a both-thresholds-zero check, so each call site keeps its own condition.
This is the expand step only. The ecstore and heal copies are untouched and are removed by the follow-up migrate task.
Refs rustfs/backlog#2047
Zhengchao An