Current reuse, TAI materialize, and TAI fused MLA store are optimized CP shared-KV paths. Their fallback helpers already emitted warnings, but the messages were not consistently grep-able with the standard CP shared-KV fallback marker.
This moves the marker into the helper layer so individual fallback call sites do not have to remember to include it, and keeps the existing per-reason rate limiting.
Constraint: Runtime fallback logs must be visible without enabling debug logging.
Rejected: Prefix only selected call sites | helper-level prefixing avoids future unmarked fallback messages.
Confidence: high
Scope-risk: narrow
Directive: New CP shared-KV runtime fallback helpers should use [CP_SHARED_KV_FALLBACK] and a component name.
Tested: Local py_compile for cp_shared_kv_runtime.py and test_cp_shared_kv_runtime.py.
Tested: Local extracted assertLogs check for all three fallback helper prefixes.
Tested: Remote g0034 pytest exact runtime helper tests: 2 passed, 3 warnings.
Not-tested: Full cp_shared_kv_runtime.py suite in this slice.
Co-authored-by: OmX <omx@oh-my-codex.dev>
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