refactor: simplify claude launch — no streaming, no output monitoring (#1412)

Replace the complex claude launch pattern (subshell + PID file + tee
pipe + stream-json + 50-line watchdog monitoring log file growth +
session-end detection) with a simple direct launch:

  claude -p "..." >> "${LOG_FILE}" 2>&1 &

The watchdog is now just a wall-clock timeout. The idle-output detection,
stream-json result parsing, and tee piping are all removed.

Also remove GitHub Actions concurrency groups — the trigger server
already handles dedup (409 for same issue, 409 for same reason), making
the GH Actions concurrency groups redundant queuing.

Changes:
- refactor.sh: simple launch + wall-clock-only watchdog
- security.sh: same simplification
- discovery.sh: same (refactored _kill_claude_process and
  _run_watchdog_loop to simpler signatures)
- All 4 workflows: remove concurrency groups

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

.github/workflows/security.yml

@@ -7,10 +7,6 @@ on:
     - cron: '*/30 * * * *'
   workflow_dispatch:
 
-concurrency:
-  group: security-${{ github.event_name == 'issues' && format('issue-{0}', github.event.issue.number) || 'scheduled' }}
-  cancel-in-progress: false
-
 jobs:
   review:
     runs-on: ubuntu-latest