analysis(matlab): add log(day) model + Cohen's f + power to every variation

Add variation_logpower.m (self-contained) + make_variation_logpower.m,
dropping logpowersim.m + logpower_result.txt into all 28 variation folders.
Matches the paper's power code: models behavior ~ stim + log(day) +
stim:log(day) + (1|rat) (log(day+1), since our day 0 = paper Day 1), reports
Cohen's f (partial eta^2 of the interaction) and the interaction under
residual/Satterthwaite/honest random-slope DF, then runs the Monte-Carlo power
sim on the log-day ground truth (per-animal cluster-honest + LME power).

Notable: under log(day) the accumulating divergence is captured more sharply,
so several full-window scenarios reach honest significance that were n.s. under
raw day (e.g. right_only_d0_13 honest p=0.003, unmerge_d0_13 0.021,
unmerge_d0_10 0.036); Cohen's f is small-medium (~0.10-0.34).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

analysis/matlab/variations/boxa_a2_d0_10/logpower_result.txt

@@ -0,0 +1,36 @@
+==============================================================================
+LOG-DAY MODEL + COHEN'S f + POWER -- boxa_a2_d0_10
+==============================================================================
+model: behavior ~ stim + log(day) + stim:log(day) + (1|rat)   (success COUNT)
+log(day) uses 1-indexed training day (our day 0 = paper "Day 1")
+observed groups: stim n=3, control n=4   nrep=120, alpha=0.05
+
+--- fitted on real data ---
+stim x log(day) interaction: F(1,68)=3.821  p(resid)=0.05474  p(Satt)=0.05451 (df=72)
+  honest per-animal random slope (log-day): F(1,14.6)=3.22  p=0.09348
+Cohen's f (interaction, partial eta^2=0.009) = 0.097  (small; f: .10 small, .25 medium, .40 large)
+
+--- power simulation (log-day ground truth: stim:logday=+8.69, ratSD=0.00, resSD=13.42) ---
+
+ true stim:log(day) = +8.69 (100% of observed)
+  N/group  | per-animal power | LME power
+  ------------------------------------------
+  3        |  0.23            |  0.47  <- observed
+  5        |  0.57            |  0.72
+  8        |  0.83            |  0.87
+  12       |  0.98            |  0.99
+  16       |  0.99            |  1.00
+  24       |  1.00            |  1.00
+
+ true stim:log(day) = +4.34 (50% of observed)
+  N/group  | per-animal power | LME power
+  ------------------------------------------
+  3        |  0.07            |  0.12  <- observed
+  5        |  0.11            |  0.19
+  8        |  0.30            |  0.38
+  12       |  0.34            |  0.40
+  16       |  0.62            |  0.64
+  24       |  0.75            |  0.78
+
+Read the per-animal column as the honest power; the LME column matches the
+paper's power code (anova interaction p, observation-level DF) and is optimistic.