add demo sources: VHS tapes, helper scripts, and tutorial

Tracks the inputs that drive `mage demo` so the GIFs and screenshots
under demo/assets/ can be reproduced from a checkout. The generated
assets themselves (~50 MB of GIFs and PNGs) are excluded via gitignore
since they're fully reproducible from the tapes in ~10 min.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/demo/scripts/workload.sh b/demo/scripts/workload.sh
new file mode 100755
index 0000000..ebbf58b
--- /dev/null
+++ b/demo/scripts/workload.sh
@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+# Background workload for demo tapes. Generates a steady mix of file I/O
+# (open/read/close), big writes (fsync/dd), stat-heavy traffic, and ioworkload
+# scenarios so every TUI tab has something interesting to display.
+#
+# Designed to be killed via `kill $!` from the tape wrapper. All children are
+# placed in this script's process group so a single signal cleans them up.
+
+set -u
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+IOWORKLOAD="${ROOT}/../ioworkload"
+SCRATCH="$(mktemp -d -t ior-demo-workload-XXXXXX)"
+trap 'rm -rf "$SCRATCH"' EXIT
+
+cleanup() {
+    trap - TERM INT
+    # Kill the entire process group so all background loops stop.
+    kill -- -$$ 2>/dev/null || true
+    exit 0
+}
+trap cleanup TERM INT
+
+# A) walk /usr and read first byte of each file: tons of openat/read/close + varied paths.
+(
+    while true; do
+        find /usr/share /usr/lib -maxdepth 4 -type f 2>/dev/null \
+            | shuf -n 800 \
+            | xargs -r -I{} sh -c 'head -c 1 "{}" >/dev/null 2>&1' || true
+        sleep 1
+    done
+) &
+
+# B) periodic large write with fsync via dd: fills the latency tab with slow writes.
+(
+    while true; do
+        dd if=/dev/zero of="${SCRATCH}/big.bin" bs=1M count=20 conv=fsync status=none 2>/dev/null || true
+        sleep 3
+        rm -f "${SCRATCH}/big.bin"
+    done
+) &
+
+# C) stat-heavy directory crawl: feeds the syscall tab with newfstatat/getdents.
+(
+    while true; do
+        find /etc /var/log -maxdepth 3 >/dev/null 2>&1 || true
+        sleep 2
+    done
+) &
+
+# D) ioworkload scenario rotation if the binary exists: gives us syscall variety
+# beyond what the shell utilities trigger (mmap, dup, fcntl, sync, rename, link).
+if [ -x "$IOWORKLOAD" ]; then
+    (
+        scenarios=(
+            open-basic
+            readwrite-basic
+            stat-basic
+            stat-statx
+            mmap-basic
+            sync-basic
+            dup-basic
+            fcntl-dupfd
+            rename-basic
+            link-basic
+            dir-basic
+        )
+        while true; do
+            for s in "${scenarios[@]}"; do
+                "$IOWORKLOAD" --scenario="$s" >/dev/null 2>&1 || true
+            done
+        done
+    ) &
+fi
+
+# Idle until killed.
+wait