Rename split-loop-with-lambda to slice-with-lambda

The refactoring is now published as Slice on sammancoaching.org:
https://sammancoaching.org/refactorings/slice.html

- git mv ideas/split-loop-with-lambda -> ideas/slice-with-lambda
- rename learning-hour file and update frontmatter name
- update paths in tools/rehearse scripts and report title
- update prose: 'Split Loop with Lambda' -> 'Slice with Lambda'
  in learning hour, exercise READMEs, storyboard, solution comments
- link the published Slice refactoring from the pattern draft

tools/rehearse/run-rehearsal.sh

@@ -13,7 +13,7 @@ SCRATCH=/tmp/rehearsal
 PRISTINE="$SCRATCH/pristine"
 RUNS_DIR="$SCRATCH/runs"
 REPO=/home/cardfanatic/qwan/exercises/learning-hour-maker
-SOLUTION="$REPO/ideas/split-loop-with-lambda/exercise/solution"
+SOLUTION="$REPO/ideas/slice-with-lambda/exercise/solution"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 CAP_SECONDS=600
 
@@ -131,7 +131,7 @@ done
 # --- combined report ---
 REPORT="$SCRATCH/report.md"
 {
-  echo "# Rehearsal report — split-loop-with-lambda ($(date -Iseconds))"
+  echo "# Rehearsal report — slice-with-lambda ($(date -Iseconds))"
   echo
   for RUN in $WHICH; do
     RUN_DIR="$RUNS_DIR/$RUN"