v0.1.9.3

v0.1.9.3 ships the first target-risk layer for ledgr.\n\nHighlights:\n- Adds classed target-risk constructors: ledgr_risk_none(), ledgr_risk_chain(), ledgr_risk_long_only(), and ledgr_risk_max_weight().\n- Threads risk identity through config hashes, committed runs, sweeps, saved sweeps, promotion context, and reopened candidates via risk_chain_hash and risk_plan_json.\n- Inserts the bounded risk slot between strategy target validation and fill timing while preserving one shared fold core.\n- Adds documentation, examples, NEWS, pkgdown reference indexing, and the v0.1.9.3 release closeout.\n\nNon-scope remains explicit: no affordability enforcement, liquidity/capacity policy, OMS behavior, broker-grade margin/shorting, arbitrary risk callbacks, walk-forward implementation, or compiled-core architecture changes.\n\nVerification: local release gate passed; branch CI, PR CI, main CI, pkgdown deploy, and tag CI are green.