Refreshes equity portfolio canvases from the latest Excel export. Launches parallel agents to update valuation, risk, macro, and daily-actions canvases. Use when the user updates their portfolio Excel file, adds holdings, wants to refresh buy/sell signals, or says "refresh my portfolio canvases", "update the stock canvases", or "re-run the portfolio analysis". Canvas basenames are configured in the user's project (e.g. portfolio-valuation-analysis, portfolio-risk-analysis, portfolio-macro-outlook, daily-stock-actions).
