fix: Migrate review-pr.sh to SDK + pr-lifecycle (#800)

Extract agent_run() into shared lib/agent-sdk.sh to eliminate code
duplication between dev-agent.sh and review-pr.sh (CI dedup check).

Rewrite review-pr.sh from tmux-based agent-session.sh to synchronous
claude -p invocations via shared agent-sdk.sh, matching the SDK pattern
from dev-agent.sh (#798).

Key changes:
- Create lib/agent-sdk.sh with shared agent_run() function
- Both dev-agent.sh and review-pr.sh now source lib/agent-sdk.sh
  instead of defining agent_run() inline
- Replace agent-session.sh (tmux + monitor_phase_loop) with agent_run()
- Add .sid file for session continuity: re-reviews resume the original
  session via --resume, so Claude remembers its prior review
- Use worktree.sh for worktree cleanup
- Remove phase file signaling — completion is automatic when claude -p
  returns
- Keep all review business logic unchanged

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/agent-sdk.sh

@@ -0,0 +1,53 @@
+#!/usr/bin/env bash
+# agent-sdk.sh — Shared SDK for synchronous Claude agent invocations
+#
+# Provides agent_run(): one-shot `claude -p` with session persistence.
+# Source this from any agent script after defining:
+#   SID_FILE  — path to persist session ID (e.g. /tmp/dev-session-proj-123.sid)
+#   LOGFILE   — path for log output
+#   log()     — logging function
+#
+# Usage:
+#   source "$(dirname "$0")/../lib/agent-sdk.sh"
+#   agent_run [--resume SESSION_ID] [--worktree DIR] PROMPT
+#
+# After each call, _AGENT_SESSION_ID holds the session ID (also saved to SID_FILE).
+# Recover a previous session on startup:
+#   if [ -f "$SID_FILE" ]; then _AGENT_SESSION_ID=$(cat "$SID_FILE"); fi
+
+set -euo pipefail
+
+_AGENT_SESSION_ID=""
+
+# agent_run — synchronous Claude invocation (one-shot claude -p)
+# Usage: agent_run [--resume SESSION_ID] [--worktree DIR] PROMPT
+# Sets: _AGENT_SESSION_ID (updated each call, persisted to SID_FILE)
+agent_run() {
+  local resume_id="" worktree_dir=""
+  while [[ "${1:-}" == --* ]]; do
+    case "$1" in
+      --resume) shift; resume_id="${1:-}"; shift ;;
+      --worktree) shift; worktree_dir="${1:-}"; shift ;;
+      *) shift ;;
+    esac
+  done
+  local prompt="${1:-}"
+
+  local -a args=(-p "$prompt" --output-format json --dangerously-skip-permissions --max-turns 200)
+  [ -n "$resume_id" ] && args+=(--resume "$resume_id")
+  [ -n "${CLAUDE_MODEL:-}" ] && args+=(--model "$CLAUDE_MODEL")
+
+  local run_dir="${worktree_dir:-$(pwd)}"
+  local output
+  log "agent_run: starting (resume=${resume_id:-(new)}, dir=${run_dir})"
+  output=$(cd "$run_dir" && timeout "${CLAUDE_TIMEOUT:-7200}" claude "${args[@]}" 2>>"$LOGFILE") || true
+
+  # Extract and persist session_id
+  local new_sid
+  new_sid=$(printf '%s' "$output" | jq -r '.session_id // empty' 2>/dev/null) || true
+  if [ -n "$new_sid" ]; then
+    _AGENT_SESSION_ID="$new_sid"
+    printf '%s' "$new_sid" > "$SID_FILE"
+    log "agent_run: session_id=${new_sid:0:12}..."
+  fi
+}