fix: load_dotenv before heavy imports in issue1586_fu_caveatfix_figures.py (thread-caps red on main)

Overview / Motivation

Filed by the #1660 orchestrator from an implementer-surfaced finding (2026-07-24): a test red on pristine origin/main, polluting every Step 9c / merge-gate baseline until fixed. NOT a workflow-surface fix — experiment-script code (#847 thread-caps class).

Goal

Bring scripts/issue1586_fu_caveatfix_figures.py into the #847 thread-caps contract (dotenv/env setdefault BEFORE heavy imports) so tests/test_shared_vm_thread_caps.py::test_no_new_torch_before_dotenv_vm_entrypoints passes on main.

Bug

• Observed: scripts/issue1586_fu_caveatfix_figures.py (landed 81d2400b05) imports matplotlib/numpy + explore_persona_space.analysis.paper_plots at module top with ZERO load_dotenv() call, so the shared-VM thread-caps setdefault (orchestrate/env.py, #847) never fires before the heavy stack initializes. The pinned invariant test_no_new_torch_before_dotenv_vm_entrypoints flags it — red on pristine main.
• Fix shape: the standard 2-line fix — from explore_persona_space.orchestrate.env import load_dotenv + load_dotenv() placed BEFORE the heavy imports (match the pattern used by sibling issue scripts that pass the invariant).
• verified-at-filing: grep -c "load_dotenv" scripts/issue1586_fu_caveatfix_figures.py → 0; module-top import matplotlib.pyplot/numpy/paper_plots at ~L27; landed commit 81d2400b05 (2026-07-24 grep + git log).

Scope

• scripts/issue1586_fu_caveatfix_figures.py only. The fix must keep figure output byte-stable (import-order change only).