Initial implementation of slider

Single-file markdown slideshow for the terminal. Parses slides split by
`---`, renders each with glow, and navigates with n/p/q or arrow keys.

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

bin/slider

@@ -0,0 +1,93 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# slider — terminal markdown slideshow
+# Usage: slider <file.md>
+
+usage() {
+    echo "Usage: slider <file.md>" >&2
+    exit 1
+}
+
+[[ $# -ne 1 ]] && usage
+file="$1"
+[[ ! -f "$file" || ! -r "$file" ]] && { echo "Error: cannot read '$file'" >&2; exit 1; }
+
+# Parse slides split on "---"
+slides=()
+current=""
+while IFS= read -r line || [[ -n "$line" ]]; do
+    if [[ "$line" == "---" ]]; then
+        [[ -n "${current// }" ]] && slides+=("$current")
+        current=""
+    else
+        current+="$line"$'\n'
+    fi
+done < "$file"
+[[ -n "${current// }" ]] && slides+=("$current")
+
+total=${#slides[@]}
+[[ $total -eq 0 ]] && { echo "No slides found in '$file'" >&2; exit 1; }
+
+# Temp file for glow rendering; cleaned up on exit
+tmpfile=$(mktemp /tmp/slider.XXXXXX.md)
+trap 'rm -f "$tmpfile"' EXIT
+
+idx=0
+
+show_slide() {
+    tput clear
+    printf "  Slide %d/%d   [n] next  [p] prev  [q] quit\n\n" $((idx + 1)) "$total"
+    printf '%s' "${slides[$idx]}" > "$tmpfile"
+    glow - < "$tmpfile"
+}
+
+show_slide
+
+while true; do
+    read -rsn1 key < /dev/tty
+    case "$key" in
+        n)
+            if (( idx < total - 1 )); then
+                idx=$(( idx + 1 ))
+                show_slide
+            else
+                tput clear
+                printf "  Slide %d/%d   [n] next  [p] prev  [q] quit\n\n" $((idx + 1)) "$total"
+                printf '%s' "${slides[$idx]}" > "$tmpfile"
+                glow - < "$tmpfile"
+                printf "\n  End of presentation — press q to quit\n"
+            fi
+            ;;
+        p)
+            if (( idx > 0 )); then
+                idx=$(( idx - 1 ))
+                show_slide
+            fi
+            ;;
+        $'\x1b')
+            read -rsn2 -t 0.1 rest < /dev/tty || true
+            if [[ "$rest" == "[C" ]]; then  # right arrow → next
+                if (( idx < total - 1 )); then
+                    idx=$(( idx + 1 ))
+                    show_slide
+                else
+                    tput clear
+                    printf "  Slide %d/%d   [n] next  [p] prev  [q] quit\n\n" $((idx + 1)) "$total"
+                    printf '%s' "${slides[$idx]}" > "$tmpfile"
+                    glow - < "$tmpfile"
+                    printf "\n  End of presentation — press q to quit\n"
+                fi
+            elif [[ "$rest" == "[D" ]]; then  # left arrow → prev
+                if (( idx > 0 )); then
+                    idx=$(( idx - 1 ))
+                    show_slide
+                fi
+            fi
+            ;;
+        q)
+            tput clear
+            break
+            ;;
+    esac
+done