feat(diagnostics): funnel events throughout setup with persisted install-id

Shared bash + node emitter in setup/lib/diagnostics.{sh,ts} reads/writes data/install-id so every event from a single install shares one distinct_id — bash-side setup_launched/setup_start, node-side auto_started, per-step started/completed, auth_method_chosen, channel_chosen, first_chat_ready/failed, setup_incomplete, setup_aborted, setup_completed. Opt-out via NANOCLAW_NO_DIAGNOSTICS=1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

setup/lib/diagnostics.sh

@@ -0,0 +1,61 @@
+# diagnostics.sh — shared PostHog emitter for bash-side setup code.
+#
+# Source this file after $PROJECT_ROOT is set:
+#
+#   source "$PROJECT_ROOT/setup/lib/diagnostics.sh"
+#   ph_event bootstrap_completed status=success platform=macos
+#
+# All emits are fire-and-forget (background curl, 3s max timeout); they
+# never fail the caller. Honors NANOCLAW_NO_DIAGNOSTICS=1. The distinct_id
+# is persisted at data/install-id so the bash + node halves of setup use
+# the same id and events from one install join into a single funnel.
+
+NANOCLAW_PH_KEY='phc_fx1Hhx9ucz8GuaJC8LVZWO8u03yXZZJJ6ObS4yplnaP'
+NANOCLAW_PH_URL='https://us.i.posthog.com/capture/'
+
+# Resolve or create the persisted install id. Echoes the id (lowercase uuid).
+# Creates data/install-id on first use. Safe to call pre-Node: uses only
+# bash + uuidgen/urandom fallback + mkdir.
+ph_install_id() {
+  local root="${NANOCLAW_PROJECT_ROOT:-${PROJECT_ROOT:-$PWD}}"
+  local f="$root/data/install-id"
+  if [ ! -s "$f" ]; then
+    mkdir -p "$(dirname "$f")" 2>/dev/null || return 0
+    local id
+    id=$(uuidgen 2>/dev/null \
+      || cat /proc/sys/kernel/random/uuid 2>/dev/null \
+      || printf 'fallback-%s-%s' "$(date +%s)" "$$")
+    printf '%s' "$id" | tr 'A-Z' 'a-z' > "$f" 2>/dev/null || return 0
+  fi
+  cat "$f" 2>/dev/null
+}
+
+# Emit a PostHog event. First arg is the event name; remaining args are
+# `key=value` pairs merged into properties. Values are JSON-escaped for
+# quotes and backslashes; keep them short and alphanumeric-ish.
+ph_event() {
+  [ "${NANOCLAW_NO_DIAGNOSTICS:-}" = "1" ] && return 0
+  local event=$1
+  shift
+  local id
+  id=$(ph_install_id)
+  [ -z "$id" ] && return 0
+
+  local props='' first=1 kv k v
+  for kv in "$@"; do
+    k="${kv%%=*}"
+    v="${kv#*=}"
+    v=${v//\\/\\\\}
+    v=${v//\"/\\\"}
+    if [ "$first" = "1" ]; then first=0; else props+=','; fi
+    props+="\"$k\":\"$v\""
+  done
+
+  local payload
+  payload=$(printf '{"api_key":"%s","event":"%s","distinct_id":"%s","properties":{%s}}' \
+    "$NANOCLAW_PH_KEY" "$event" "$id" "$props")
+
+  curl -sS --max-time 3 -X POST "$NANOCLAW_PH_URL" \
+    -H 'Content-Type: application/json' \
+    -d "$payload" >/dev/null 2>&1 &
+}