ledgr 0.2.2

ledgr 0.2.2 makes long-window, point-in-time portfolio research a complete
public workflow.

Highlights:

• causal history frames and identified matrices for runs, sweeps and
  walk-forward evaluation;
• point-in-time universes, corporate actions, terminal outcomes and explicit
  missing-data assumptions;
• declarative monthly, weekly, weekday, month-day and explicit-date strategy
  schedules;
• a substantially faster and leaner long-window execution path; and
• current-only schema 124, snapshot hash rule 4 and run identity rule 4.

Upgrade notes:

• DuckDB 2.0.0 or later is required;
• rebuild snapshots, experiment stores, saved sweeps and walk-forward
  artifacts created by older ledgr releases; and
• this release remains daily/session-based and long-only in its taught
  portfolio-construction workflow.

Halts and untraded sessions that a data source encodes as zero-volume bars
carrying the previous close, as the reference Sharadar data does, are still
read as observed prices: they can fill and they bypass valuation ageing and
freezing.

See the complete upgrade guide and release notes in
NEWS.md.