fix(driver/postgres): clamp reltuples -1 to 0 in inspect output

A table that has never been ANALYZEd reports reltuples = -1; surfacing that
as a negative row estimate in 'siphon inspect' reads as a bug. GREATEST(...,0)
clamps it to 0 (the conventional 'unknown/0' shown by pg tooling) while real
counts pass through unchanged. Query structure (and the s. alias fix for the
relname ambiguity) is otherwise unchanged — the 'simplify' half of the review
note is intentionally not taken, to avoid regressing the just-fixed SQL.

Author: nixrajput

internal/driver/postgres/inspect.go

@@ -9,11 +9,13 @@ import (
 // inspectQuery lists user tables with row estimates and on-disk sizes.
 // schemaname/relname are qualified with the pg_stat_user_tables alias (s.)
 // because pg_class (c) also exposes a relname column — an unqualified
-// reference is ambiguous (SQLSTATE 42702).
+// reference is ambiguous (SQLSTATE 42702). reltuples is -1 for a table that
+// has never been ANALYZEd; GREATEST clamps that to 0 so the row estimate is
+// never reported as a negative number.
 const inspectQuery = `
 SELECT
   s.schemaname || '.' || s.relname AS name,
-  COALESCE((SELECT reltuples::bigint FROM pg_class WHERE oid = c.oid), 0) AS rows,
+  GREATEST(COALESCE((SELECT reltuples::bigint FROM pg_class WHERE oid = c.oid), 0), 0) AS rows,
   pg_total_relation_size(c.oid) AS size_bytes
 FROM pg_stat_user_tables s
 JOIN pg_class c ON c.oid = s.relid