fix: add SKILLOPT_SLEEP_PYTHON override + lookback_hours first-run fallback

Two fixes from issue #57 feedback:

1. run-sleep.sh: support SKILLOPT_SLEEP_PYTHON env var to explicitly set
   the Python interpreter. Useful on macOS where system Python is 3.9 but
   a newer Python is available elsewhere (e.g. Codex Desktop's bundled
   Python 3.12). Applied to both the shared runner and the bundled
   Claude Code plugin copy.

2. cycle.py: on first run (no prior harvest recorded), apply the
   lookback_hours config (default 72h) as a time cutoff. Previously,
   first run scanned the entire transcript history, which could trigger
   massive LLM mining on users with months of session data.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plugins/claude-code/scripts/run-sleep.sh

@@ -30,12 +30,17 @@ if [ -z "${REPO_ROOT:-}" ]; then
 fi
 
 PY=""
-for cand in python3.12 python3.11 python3.10 python3; do
-  if command -v "$cand" >/dev/null 2>&1; then
-    ver="$("$cand" -c 'import sys; print("%d%d" % sys.version_info[:2])' 2>/dev/null || echo 0)"
-    if [ "${ver:-0}" -ge 310 ]; then PY="$cand"; break; fi
-  fi
-done
+# Allow explicit Python override (useful on macOS with old system Python).
+if [ -n "${SKILLOPT_SLEEP_PYTHON:-}" ]; then
+  PY="$SKILLOPT_SLEEP_PYTHON"
+else
+  for cand in python3.12 python3.11 python3.10 python3; do
+    if command -v "$cand" >/dev/null 2>&1; then
+      ver="$("$cand" -c 'import sys; print("%d%d" % sys.version_info[:2])' 2>/dev/null || echo 0)"
+      if [ "${ver:-0}" -ge 310 ]; then PY="$cand"; break; fi
+    fi
+  done
+fi
 if [ -z "$PY" ]; then
   echo "[sleep] ERROR: need Python >= 3.10 (found none)." >&2
   exit 1

plugins/run-sleep.sh

@@ -30,12 +30,17 @@ if [ -z "${REPO_ROOT:-}" ]; then
 fi
 
 PY=""
-for cand in python3.12 python3.11 python3.10 python3; do
-  if command -v "$cand" >/dev/null 2>&1; then
-    ver="$("$cand" -c 'import sys; print("%d%d" % sys.version_info[:2])' 2>/dev/null || echo 0)"
-    if [ "${ver:-0}" -ge 310 ]; then PY="$cand"; break; fi
-  fi
-done
+# Allow explicit Python override (useful on macOS with old system Python).
+if [ -n "${SKILLOPT_SLEEP_PYTHON:-}" ]; then
+  PY="$SKILLOPT_SLEEP_PYTHON"
+else
+  for cand in python3.12 python3.11 python3.10 python3; do
+    if command -v "$cand" >/dev/null 2>&1; then
+      ver="$("$cand" -c 'import sys; print("%d%d" % sys.version_info[:2])' 2>/dev/null || echo 0)"
+      if [ "${ver:-0}" -ge 310 ]; then PY="$cand"; break; fi
+    fi
+  done
+fi
 if [ -z "$PY" ]; then
   echo "[sleep] ERROR: need Python >= 3.10 (found none)." >&2
   exit 1

skillopt_sleep/cycle.py

@@ -144,6 +144,14 @@ def run_sleep_cycle(
         _progress(cfg, f"using {len(tasks)} seeded tasks")
     else:
         since = state.last_harvest_for(project)
+        # On first run (no prior harvest), apply lookback_hours so we don't
+        # scan the entire transcript history and trigger massive LLM mining.
+        if since is None:
+            lookback_hours = cfg.get("lookback_hours", 72)
+            if lookback_hours and lookback_hours > 0:
+                import time
+                cutoff = time.time() - lookback_hours * 3600
+                since = _now_iso(cutoff)
         max_tasks = cfg.get("max_tasks_per_night", 40)
         max_sessions = cfg.get("max_sessions_per_night", 0) or max_tasks * 3
         candidate_limit = max_tasks