Build out all 27 modules + capstone (#1)

Co-authored-by: claude <claude@jpaul.io>
Co-committed-by: claude <claude@jpaul.io>

modules/06-branches-sandboxes-for-experiments/lab/make-conflict.sh

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+#!/usr/bin/env bash
+#
+# make-conflict.sh — manufacture a guaranteed merge conflict to practice on.
+#
+# AI edits are nondeterministic, so the lab's organic conflict (two branches editing the same usage
+# line in cli.py) doesn't ALWAYS land. This script guarantees one: it creates two branches that each
+# append a different line to the same spot in README.md, then leaves you mid-merge with a real
+# conflict in your working tree. The resolution mechanic is identical to the code case in the lab —
+# read the <<<<<<< / ======= / >>>>>>> markers, edit to the version you want, remove the markers,
+# then `git add` + `git commit`.
+#
+# Run it from anywhere inside your tasks-app repo:
+#     bash modules/06-branches-sandboxes-for-experiments/lab/make-conflict.sh
+#
+# It is non-destructive to your real work: it only touches README.md on two throwaway practice
+# branches and refuses to run if your working tree is dirty.
+
+set -euo pipefail
+
+BRANCH_A="practice/conflict-a"
+BRANCH_B="practice/conflict-b"
+FILE="README.md"
+
+# 1. Must be inside a Git repo.
+if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
+  echo "error: not inside a Git repository. cd into your tasks-app first." >&2
+  exit 1
+fi
+
+# 2. Working tree must be clean, or switching branches would clobber uncommitted work.
+if ! git diff --quiet || ! git diff --cached --quiet; then
+  echo "error: you have uncommitted changes. commit or stash them first (git status)." >&2
+  exit 1
+fi
+
+# 3. README.md must exist (it ships with the Module 1 tasks-app).
+if [ ! -f "$FILE" ]; then
+  echo "error: $FILE not found. run this from your tasks-app repo root." >&2
+  exit 1
+fi
+
+# 4. Remember where we started, and clean up any leftover practice branches from a prior run.
+START_BRANCH="$(git rev-parse --abbrev-ref HEAD)"
+git branch -D "$BRANCH_A" >/dev/null 2>&1 || true
+git branch -D "$BRANCH_B" >/dev/null 2>&1 || true
+
+# 5. Branch A: append one version of a line, commit.
+git switch -c "$BRANCH_A" >/dev/null
+printf '\n<!-- practice line: KEEP THE LEFT VERSION -->\n' >> "$FILE"
+git add "$FILE"
+git commit -q -m "practice: append line (branch A)"
+
+# 6. Branch B (off the original branch): append a DIFFERENT version to the same spot, commit.
+git switch "$START_BRANCH" >/dev/null
+git switch -c "$BRANCH_B" >/dev/null
+printf '\n<!-- practice line: KEEP THE RIGHT VERSION -->\n' >> "$FILE"
+git add "$FILE"
+git commit -q -m "practice: append line (branch B)"
+
+# 7. Merge A into B to trigger the conflict. Disable the editor so it doesn't block.
+echo
+echo "Merging $BRANCH_A into $BRANCH_B to create a conflict..."
+set +e
+GIT_EDITOR=true git merge "$BRANCH_A" >/dev/null 2>&1
+set -e
+
+echo
+echo "================================================================"
+echo " A merge conflict now exists in: $FILE"
+echo " You are on branch: $BRANCH_B"
+echo "================================================================"
+echo
+echo " Next steps (the skill you're practicing):"
+echo "   1. git status                # see $FILE under 'Unmerged paths'"
+echo "   2. open $FILE and find the <<<<<<< / ======= / >>>>>>> markers"
+echo "   3. edit it to the version you want; delete all three marker lines"
+echo "      (or ask your editor-integrated AI to resolve it, then verify)"
+echo "   4. git add $FILE"
+echo "   5. git commit              # completes the merge"
+echo
+echo " Chicken out? Undo the whole thing with:  git merge --abort"
+echo
+echo " When you're done practicing, clean up the throwaway branches:"
+echo "   git switch $START_BRANCH"
+echo "   git branch -D $BRANCH_A $BRANCH_B"
+echo