`decimal` is stored as exact TEXT, but SQLite has no native decimal type,
so arithmetic/aggregation implicitly coerces it to an IEEE-754 double.
The computed result carries no playground type, so `sum(price * qty)`
rendered the double's full noise — `298.59999999999997` for `298.60` — a
confusing, off-topic float lesson for a teaching tool.
Add `format_real_display`: round REAL values to 15 significant figures
(a double's reliable precision) then take the shortest round-tripping
form, collapsing `298.59999999999997` to `298.6`. Wired into `format_cell`
(result-set / `show data` cells) only — the sole surface where the noise
appears, since it arises from arithmetic.
Every other f64->string path keeps full precision for semantic, not
cosmetic, reasons: CSV persistence stays byte-exact for round-trip;
`render_value` is a canonical identity key for the uniqueness dry-runs
(dry_run_unique, check_uniqueness_collisions), where rounding would
report collisions the exact-valued engine wouldn't; FK-key matching and
EXPLAIN-SQL literals likewise stay exact.
ADR-0005 Amendment 1; +7 tests.
claude@clouddev1
3d4a0fd45e