Problem

EXPLAIN output in rpg is currently rendered as plain text — same as psql. For a DBA tool, this is a missed opportunity. The plan is hard to scan at a glance.

Goal

Make EXPLAIN output readable at terminal speed. Inspired by the PostgreSQL EXPLAIN dialect in Pygments (https://pygments.org/docs/lexers/#pygments.lexers.sql.PostgresExplainLexer) — borrow the token grammar and apply terminal colors.

Proposed visualization

Color-code the key elements:

• Node type (Seq Scan, Index Scan, Hash Join, etc.) — bold/cyan
• Cost () — dim, not important unless high
• Actual time () — color-coded: green <10ms, yellow <100ms, red >100ms
• Rows — highlight when estimate vs actual diverge significantly (>10x)
• Filter / Index Cond — highlight in yellow (potential optimization target)
• Buffers — highlight high shared_hit_blocks in a different shade
• Nested loop with high loops — flag visually

The raw text structure (indentation, arrows) must be preserved — we only add color, never reformat.

Reference

• Pygments PostgreSQL EXPLAIN lexer: https://github.com/pygments/pygments/blob/master/pygments/lexers/sql.py (search for PostgresExplainLexer)
• Study the token patterns — port them to Rust regex in src/explain/ (no Python dependency)

Implementation hints

• New module or extend src/explain/
• Apply coloring only when stdout is a TTY (same guard as other highlighting)
• Respect --no-highlight / no_highlight setting
• Works for both inline EXPLAIN queries and the /explain AI command output

Acceptance criteria

• Node types, costs, actual times, and filters are visually distinct
• High row-estimate divergence (>10x) is highlighted
• Coloring disabled correctly when --no-highlight is set or stdout is not a TTY
• Tests for the highlighter (unit tests with sample EXPLAIN output strings)
• Screenshot/recording in PR showing before/after