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jgrusewski d6eca73e52 feat(dqn): #212 — intent-side magnitude distribution HEALTH_DIAG metric
Adds intent_dist_q/h/f alongside eval_dist_q/h/f to separate policy-
learning quality from Kelly-enforcement reality. Per memory pearl
project_magnitude_eval_collapse_kelly_capped.md: EVAL_DIST Quarter
dominance is a downstream artefact of Kelly cap × warmup_floor ×
safety_multiplier math, NOT a policy-learning failure. The intent
metric exposes the policy's pre-Kelly-cap chosen mag bucket so
operators can distinguish "policy isn't learning Full" from "Kelly
cap is suppressing Full" — the latter being an operationally-correct
state during cold-start positions.

Pure observability: no Kelly-math tweaks, no new tuned constants, no
reward-bias mechanisms (all explicitly forbidden by the memory pearl).
The intent_mag bucket comes straight from the factored action's
mag_idx (0/1/2) which already maps 1:1 to Quarter/Half/Full buckets.
The pre-cap mag_idx is already captured by the action-select kernel
into intent_mag_buf and exposed via the trainer's pre-existing
last_eval_intent_magnitude_dist host field — this commit only wires
that signal into HEALTH_DIAG.

Wired through (one coordinated commit per feedback_no_partial_refactor):
  - health_diag.rs: HealthDiagSnapshot gains intent_dist_q/h/f fields
    adjacent to eval_dist_*; size assertion bumped 147 → 150 fields.
  - health_diag_kernel.cu: 3 new WORD_INTENT_DIST_* slots at [77..80);
    every downstream WORD_* shifted by +3 in lockstep; WORD_TOTAL +
    static_assert bumped 147 → 150. (The slots are reserved identically
    to WORD_EVAL_DIST_* — both currently inert; HEALTH_DIAG GPU port
    Phases 2/3 will populate them in lockstep with their sibling slots.)
  - training_loop.rs: new adjacent tracing::info!() emitting
    "intent_dist [iq=... ih=... if=...]" from the existing host-side
    last_eval_intent_magnitude_dist field, immediately after the big
    HEALTH_DIAG line containing eval_dist [eq=... eh=... ef=...].
  - docs/dqn-wire-up-audit.md: new top-of-file entry per Invariant 7.

Behavior: zero change. Only adds observability.

Verification:
  - cargo check -p ml --offline: clean.
  - cargo test -p ml --lib --offline -- health_diag: 3/3 pass.
  - cargo test -p ml --test sp4_producer_unit_tests --release
    --ignored: 16/16 GPU tests pass.

Closes #212.
2026-05-01 17:11:19 +02:00
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