BacktestHarness now owns a PerceptionTrainer (in inference role) instead
of a raw CfcTrunk. The sliding K-window of recent snapshots accumulates
in the harness; at each decision-stride boundary (and only once the
window has reached cfg.seq_len), the harness calls
trainer.forward_only(&window) and broadcasts the last K position's
per-horizon probs to the LobSim.
fxt-backtest's main.rs constructs the trainer via
PerceptionTrainer::from_checkpoint when --checkpoint is supplied (else
random init for noise baseline).
Why this shape: PerceptionTrainer's evaluate_batched already runs the
full inference chain (snap → vsn → mamba2 → ln → mamba2 → ln →
attn_pool → cfc K-loop → grn heads) correctly. Duplicating that 400-line
forward chain on CfcTrunk would double the surface area for the same
result — the trunk's role is weight-source-of-truth (achieved in X1-X9),
not kernel-launch orchestration.
End-to-end status: alpha_train emits Checkpoint files via X14 wiring;
fxt-backtest now loads those Checkpoints via from_checkpoint and drives
forward via forward_only. Phase 2 (Argo runtime: training → smoke →
threshold pre-reg → 560-cell deployability sweep → verdict) is unblocked.
Adds PerceptionTrainer::config() accessor so the harness can read seq_len.
Verification: ml-alpha + ml-backtesting + fxt-backtest all build clean.
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