skills: pi-subagent, extracted from pi-review-panel, which now runs on it

The panel's mechanics -- headless pi runs that don't hang, answer
extraction, billed cost, retries, verifying what comes back -- are not
review-specific. pi-subagent covers one delegated task, one brief fanned out
to several models, or a job split into parallel parts; pi-review-panel keeps
only what a review adds.

run-agent.sh replaces run-member.sh and fixes what it got wrong:

- `timeout` is not on a Mac without coreutils, which failed every member
  with exit 127; it falls back to gtimeout, then perl's alarm (142 -> 124).
- pi exits 0 when the provider refuses the request, or the answer is empty;
  both are now exit 1, with stopReason and error in the cost file.
- a retry moves the earlier attempt to <name>.attempt<N>.* instead of
  overwriting its cost file.

New options: --tools (an allowlist; read,grep,find,ls is read-only by
construction), --cwd, --context-files, --brief, --deliver. status.sh
replaces the `pgrep -f run-member.sh` loop, which counted every panel on the
machine, and prints the cost table.

From dot request 20261021-114826-work-laptop-2b868c.

1 files changed, 85 insertions, 0 deletions

diff --git a/skills/pi-subagent/status.sh b/skills/pi-subagent/status.sh
new file mode 100755
index 0000000..15a75de
--- /dev/null
+++ b/skills/pi-subagent/status.sh
@@ -0,0 +1,85 @@
+#!/bin/bash
+# Report on the subagents of one workdir: what is still running, and the
+# cost table of everything that finished, failed attempts included.
+#
+#   status.sh <workdir>                 report once
+#   status.sh --wait [secs] <workdir>   report every <secs> (default 60) until
+#                                       nothing is running, then the table
+#
+# Exit status: 0 when nothing is running, 3 while something still is.
+#
+# "Running" means <workdir>/out/<name>.running exists and its PID is alive. A
+# marker whose process is gone (run-agent.sh was killed) is reported as stale
+# and removed.
+
+set -u
+
+wait=""; interval=60
+if [[ "${1:-}" == "--wait" ]]
+then
+  wait=y; shift
+  if [[ "${1:-}" =~ ^[0-9]+$ ]]; then interval="$1"; shift; fi
+fi
+P="${1:?workdir}"
+out="$P/out"
+
+running() {
+  local marker pid alive=()
+  for marker in "$out"/*.running
+  do
+    [[ -e "$marker" ]] || continue
+    pid="$(cat "$marker" 2>/dev/null)"
+    if [[ -n "$pid" ]] && kill -0 "$pid" 2>/dev/null
+    then
+      alive+=("$(basename "$marker" .running)")
+    else
+      echo "stale: $(basename "$marker" .running) (process gone)" >&2
+      rm -f "$marker"
+    fi
+  done
+  echo "${alive[*]:-}"
+}
+
+free_gb() {
+  df -k "$P" | awk 'NR==2 {printf "%.1f", $4/1048576}'
+}
+
+if [[ -n "$wait" ]]
+then
+  while :
+  do
+    names="$(running)"
+    [[ -z "$names" ]] && break
+    echo "$(date +%H:%M:%S) running=$(wc -w <<< "$names" | tr -d ' ') freeGB=$(free_gb): $names"
+    sleep "$interval"
+  done
+fi
+
+names="$(running)"
+if [[ -n "$names" ]]
+then
+  echo "running: $names"
+fi
+
+shopt -s nullglob
+costs=("$out"/*.cost.json)
+if [[ ${#costs[@]} -gt 0 ]]
+then
+  {
+    echo -e "name\tprovider\tmodel\texit\tstop\tsecs\tturns\tin\tout\tanswer_bytes\tcost"
+    for f in "${costs[@]}"
+    do
+      n="$(basename "$f" .cost.json)"
+      bytes=0
+      [[ -e "$out/$n.md" ]] && bytes="$(wc -c < "$out/$n.md" | tr -d '[:space:]')"
+      jq -r --arg b "$bytes" '[.name,.provider,.model,(.exit|tostring),(.stopReason // "-"),(.seconds|tostring),
+             (.turns|tostring),(.input|tostring),(.output|tostring),$b,
+             (.cost*10000|round/10000|tostring)] | @tsv' "$f" 2>/dev/null \
+        || echo -e "$n\t?\t?\t?\t?\t?\t?\t?\t?\t$bytes\t(unreadable cost file)"
+    done | sort -t$'\t' -k11 -rn
+  } | column -t -s$'\t'
+  jq -s -r '"runs: \(length)  failed: \(map(select(.exit != 0)) | length)  total cost: $\(map(.cost) | add | .*10000 | round/10000)"' \
+    "${costs[@]}" 2>/dev/null
+fi
+
+[[ -z "$names" ]] || exit 3