Constant KNOWN_PREFIXES 

pub const KNOWN_PREFIXES: &[&str];

Canonical list of well-known service-credential prefixes.

This is the single source of truth for the prefix set. Two consumers:

1. known_prefix_confidence_floor (this module) lifts any credential starting with one of these to a 0.8 confidence floor.
2. context::inference::{is_sequential_placeholder, is_hex_sequential_placeholder} strip these prefixes before sequence-detection so a ghp_aaaaaaaaaa placeholder still triggers the all-same-char suppression on the BODY, not on the prefix.

Pre-2026-05-24 state: this list was duplicated three times across confidence/prefixes.rs + context/inference.rs × 2, and the copies had already drifted (KNOWN_PREFIXES missed glcbt-, glrt-, xoxs-, vercel_, sbp_, 0x, rk_test_, sk-; the inference copies missed PRIVATE KEY, -----BEGIN, TESTKEY_). Consolidated here (kimi-dedup audit rows #12-13).