Guard zero-equity weight target translation

[Pigbibi]

Summary

• convert zero-equity weight decisions into value-mode no_execute plans before target translation
• keep weight translation annotations for diagnostics while preventing total_equity=0 validation errors
• add regression coverage for empty/new accounts

Validation

• PYTHONPATH=.:../QuantPlatformKit/src:../UsEquityStrategies/src:../HkEquityStrategies/src uv run --no-project --with pytest --with pandas pytest tests/test_decision_mapper.py -q
• PYTHONPATH=.:../QuantPlatformKit/src:../UsEquityStrategies/src:../HkEquityStrategies/src uv run --no-project --with ruff ruff check decision_mapper.py tests/test_decision_mapper.py

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve holdings for blocked zero-equity plans

When a margin or loan-backed account reports total_equity <= 0 while still holding strategy symbols, this branch converts the blocked weight decision into zero-dollar targets. The generated plan does not carry a consumable no_execute guard for execution; the rebalance loop reads allocation["targets"] and sells whenever target_values[symbol] - market_values[symbol] is below the threshold (application/execution_service.py:606, application/execution_service.py:693). Previously this input failed before any executable plan was produced, but now it can submit liquidation sells for those symbols. For a no-execute fallback, keep current market values as targets or add an execution block that downstream code actually honors.

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