feat(pgsql): diff against the live database by default for direct output

Direct pgsql output (job output.conn_env, merge --output-conn) now reads the live
schema and executes only the differences. full_ddl: true (job option) or --full-ddl
(merge) restores the full idempotent DDL; file output is unchanged.

- compare PKs by columns, skip constraint-backed indexes, normalize index method,
  FK actions, serial/numeric types, default literals/casts and truncated names
- diff table and column comments instead of re-emitting them
- remove leftover ZZDUMP debug code

pkg/jobs/jobs.go

@@ -285,11 +285,14 @@ type Options struct {
 	Types           string `yaml:"types"`
 	ArrayNullable   string `yaml:"array_nullable"`
 	ContinueOnError bool   `yaml:"continue_on_error"`
-	SkipRelations   bool   `yaml:"skip_relations"`
-	SkipEnums       bool   `yaml:"skip_enums"`
-	SkipViews       bool   `yaml:"skip_views"`
-	SkipDomains     bool   `yaml:"skip_domains"`
-	SkipSequences   bool   `yaml:"skip_sequences"`
+	// FullDDL makes direct pgsql output execute the full idempotent DDL instead of
+	// diffing against the live database first.
+	FullDDL       bool `yaml:"full_ddl"`
+	SkipRelations bool `yaml:"skip_relations"`
+	SkipEnums     bool `yaml:"skip_enums"`
+	SkipViews     bool `yaml:"skip_views"`
+	SkipDomains   bool `yaml:"skip_domains"`
+	SkipSequences bool `yaml:"skip_sequences"`
 }
 
 // Dir returns the directory that a job's relative paths resolve against: