fix(cli): a generated migration carries the column DEFAULT driver-sql puts on the same field

.changeset/generator-declared-column-default.md

@@ -0,0 +1,51 @@
+---
+"@objectstack/cli": patch
+---
+
+fix(cli): a generated migration carries the column DEFAULT `driver-sql` puts on the same field (#16294)
+
+## What was wrong
+
+Neither `os generate migration` format read a field's `defaultValue`, so a table
+created from a generated migration had no column DEFAULT where the platform's
+own table has one. A row inserted out of band — by a database client, a seed
+script, anything that does not go through the engine — got NULL where the
+declared value belonged.
+
+Driven on live PostgreSQL 16.13: one object, three schemas, one producer each
+(`driver-sql` through `initObjects`, `--format sql` through `db.raw`,
+`--format ts` by importing the emitted module and calling `up(db)`), with
+`information_schema.columns` read back per schema.
+
+```
+field                driver                          sqlgen               verdict
+f_default            null=YES default='hello'::text  null=YES default=-   DIVERGED
+f_default_required   null=YES default='hello'::text  null=YES default=-   DIVERGED
+```
+
+After: `diverged: 0 of 6` on the card's probe, and 22 of 23 on a wider one
+covering every `defaultValue` shape.
+
+## What changed
+
+Both formats now render one shared verdict, taken from
+`SqlDriver.applyDeclaredColumnDefault` — the single place a `defaultValue`
+becomes DDL on the platform side:
+
+- a **literal** is emitted, quoted the way knex binds it (`DEFAULT '42'`, not
+  `DEFAULT 42` — PostgreSQL keeps those two textually apart forever in
+  `column_default`, and the driver's column carries the quoted form);
+- **`'NOW()'`** becomes the driver's own translation, which is type-branched:
+  `CURRENT_TIMESTAMP` on a timestamp column, and a UTC-pinned expression on
+  `date` / `time`, because a bare `CURRENT_TIMESTAMP` resolves those in the
+  server's timezone;
+- **any other runtime token** (`current_user`), an **Expression envelope** and
+  an **option-level `default: true`** emit nothing, each because the driver
+  emits nothing — the engine owns those, and a column DEFAULT would override a
+  decision it makes deliberately;
+- a **`multiple: true`** field gets neither, because `createColumn` returns
+  before both questions.
+
+No authorable key, export or accepted-input set changes: `defaultValue` was
+already declared, already parsed and already honoured by the driver. The
+generators simply now read it.

content/docs/protocol/objectql/types.mdx

@@ -508,6 +508,15 @@ directly. `datetime` on PostgreSQL/MySQL keeps the native `now()`, which is
 already UTC — the driver pins every MySQL connection with
 `SET time_zone = '+00:00'`.
 
+Both `os generate migration` formats reproduce the PostgreSQL arm of this
+translation, so a table built from a generated migration carries the same
+default as one the driver creates. That holds for a plain literal
+`defaultValue` too — and for the two shapes that deliberately get **no** column
+default on either producer, because the engine resolves them per insert:
+`defaultValue: 'current_user'` (which must stay unset when there is no
+authenticated user) and an Expression envelope (`{ dialect, source }`). An
+option-level `default: true` on a `select` is likewise engine-only.
+
 <Callout type="warn">
 A DDL default only governs **newly created** columns. A column created before
 this convention keeps its legacy default and can still emit a zone-naive value on