Update to SQL Copilot

{
  "description": "Review NULL logic, time windows, timezone conversions, casts and decimal behavior.",
  "included_files": [],
  "name": "null-and-time-semantics",
  "skill_md_contents": "---\nname: null-and-time-semantics\ndescription: Review NULL logic, time windows, timezone conversions, casts and decimal behavior.\n---\n\n# Null And Time Semantics\n\n**Trigger:** Review NULL logic, time windows, timezone conversions, casts and decimal behavior.\n\n## Workflow\n1. Identify nullable input columns and differentiate unknown, missing and intentionally blank values.\n2. Check `=` vs `IS NULL`, `NOT IN` when subqueries contain NULL, CASE branching and null-safe comparisons by dialect.\n3. Define whether date windows use event, business or ingest time; use `[start, end)` timestamp boundaries when appropriate and justify local-time conversions.\n4. Verify identifier types (keep leading zeros as text), decimal arithmetic, overflow, implicit casts and collation/case sensitivity.\n5. Provide boundary examples and tests for midnight, DST transition, missing values and nonnumeric strings when relevant.\n\n## Critical standard\nNever assume string timestamps are UTC or treat every null as zero.\n\n## Evidence and execution\nOnly say \"executed\", \"passed\", \"observed\", \"optimized\" or \"deployed\" when a connected tool returned evidence for that claim. An SQL draft, a textual review, or local fixture proof alone is not production validation. Never ask the user to paste passwords or raw confidential records.\n\n## Supporting references\n- Read `../../references/null-time-types.md` when relevant.\n- Read `../../references/dialects.md` when relevant.\n\n## Return\nRevised SQL plus a short boundary-case table.\n"
}