TMComposites gate: per-gun confidence faithful for 3 guns; no pair composes

Adds a per-sample intrinsic-confidence field (GunPrediction.confidence,
threaded through FeedbackEvent/VirtualBullet, populated by Pattern, DecayGF,
KNN, GuessFactor, Tsetlin, TMHorizon) and an offline recorder + analyzer that
reproduce the paper's Figure 2 per gun and its Eq-8 composite.

Measured on 3 held-out tr-bridge DrussGT battles (33k ticks, ~133k samples/gun):
- FAITHFUL: DecayGF (rho +0.133), KNN (+0.090), Pattern (+0.064, weak).
- GuessFactor is ANTI-faithful (rho -0.067); Tsetlin c_max is useless (0.001).
- No pair of guns specialises complementarily: the same gun dominates both
  high-confidence slices in every pair.
- Eq-8 alpha-normalised confidence-weighted composite: 18.41% vs Pattern
  20.45% (McNemar p=3.1e-126). Faithful-only variant 18.68%, still loses.
  Shuffle control passes weakly (composite > shuffle, p=4e-14) so ~0.7pp of
  competence is real but ~2pp short. Offline veto: design is dead.

See docs/tmcomposites_gate.md.

common_libs/gun_harness/gun_interface.nim

@@ -35,6 +35,14 @@ type
   GunPrediction* = object
     ## Absolute (x, y) where the gun predicts the enemy will be.
     x*, y*: float
+    confidence*: float
+      ## The gun's INTRINSIC, per-sample confidence in THIS prediction, on any
+      ## positive scale the gun likes (the TMComposites gate normalises it by
+      ## the sample range, Eq 7). 0.0 means "this gun has no confidence signal"
+      ## (every deterministic geometric gun): such a gun casts no composite
+      ## vote. Deliberately NOT a rolling hit-rate: that is the selector
+      ## mechanism already measured negative (docs/gun_rack_analysis.md).
+      ## See docs/tmcomposites_gate.md and common_libs/tests/measure_tmcomposites.nim.
 
   FeedbackEvent* = object
     ## Outcome of a resolved virtual bullet.
@@ -45,6 +53,7 @@ type
     powerBin*:    int    ## index into PowerBins the bullet belongs to
     missDistance*: float  ## px; < BotRadius = hit
     hit*:         bool
+    confidence*:  float  ## copied from the spawn-time GunPrediction (above)
 
 proc bulletSpeed*(power: float): float {.inline.} =
   20.0 - 3.0 * power