refactor(b12): decision_mapper → QPK semantics/display facade (parity-tested)

[Pigbibi]

Summary (B12 consumer batch — Firstrade)

• decision_mapper.py now builds ValueTargetExecutionSemantics + ValueTargetDisplayAnnotations and calls build_value_target_execution_runtime_plan(semantics=, display=) (QPK #654/#655).
• Removed production use of build_value_target_runtime_plan, mixed ValueTargetExecutionAnnotations(...) and build_value_target_execution_annotations.
• QPK pin 350dd38 → 155d74a (same pin Schwab / Binance already run). The facade does not exist at 350dd38.
• QPK compat facade is kept; nothing removed from QPK.

Behavior parity

• Golden plans tests/fixtures/value_target_plan_parity.json (9 cases: full/legacy-key annotations, default threshold, weight translation incl. cash-only off, zero-equity block with/without holdings, no_execute, reserved-cash policy cap, risk-control execution fields, cash_by_currency) were generated on main@a314852 + QPK@350dd38 (legacy path).
• New path + QPK@155d74a reproduces the golden output exactly (canonical JSON sha256 df0420c1…e896 before and after).
• Per-case differential test also routes the same inputs through the retained QPK compat facade and asserts equality.
• Full suite: 864 passed locally with the installed pinned QPK (sibling ../QuantPlatformKit/src hidden).

QPK delta 350dd38..155d74a reviewed for Firstrade

• common/execution_translation.py, strategy_contracts.py, presentation/*: facade split; legacy path delegates (covered by parity above).
• longbridge/auth.py (#653): not imported by Firstrade.
• strategy_lifecycle AI/watch/research modules: not imported (FT uses only performance_monitor, live_equity, unchanged).
• execution_kernel (#657): new, unused.

Not in scope

No deploy / env / secret / traffic change. No Firstrade sync/session/claim/ingress change. Deploys remain manual workflow_dispatch; last 15 main commits show only github-actions checks (no Cloud Build app).

Author: Pigbibi.