feat: add iterator flashcards, sync script, and project scaffolding

- iterator.org: C++ iterator flashcard deck
- questions.org: LeetCode question index (217, 242)
- inbox.org: learning inbox with two-sum implementation and notes
- sync-anki.sh: batch sync org files to Anki via emacsclient
- AGENTS.md: conventions for AI agents working in this repo

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sync-anki.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Sync org files to Anki using emacsclient
+
+set -euo pipefail
+
+FILES=(
+    "org/cpp/iterator.org"
+    "org/cpp/containers.org"
+    # add more files here
+)
+
+for file in "${FILES[@]}"; do
+    if [[ -f "$file" ]]; then
+        echo "Syncing $file..."
+        emacsclient --eval "(progn (find-file \"$file\") (org-anki-sync-all))"
+    else
+        echo "File not found: $file" >&2
+    fi
+done
+
+echo "Done."