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

docs/JOB_FILES.md

@@ -187,6 +187,8 @@ jobs:
       format: pgsql
       path: build/schema.sql                   # file output, OR:
       conn_env: TARGET_DB_URL                  # execute against DB (pgsql only)
+                                               # default: reads live DB, executes only the diff
+                                               # (file output = full DDL); set options.full_ddl to force full DDL
       overwrite: false                         # default false
     options:
       flatten_schema: false
@@ -195,6 +197,7 @@ jobs:
       types: sqltypes                           # Bun/GORM nullable types: baselib|stdlib|sqltypes
       array_nullable: pointer_slice             # Bun: slice|pointer_slice
       continue_on_error: false                 # pgsql / scripts-exec output
+      full_ddl: false                          # pgsql database output: true = run full DDL; default diffs against live DB
       skip_relations: false                    # merge only
       skip_enums: false
       skip_views: false