# Two-phase refactor — slice 11 (imports)

Branch `ast-stage-c`.  Suite **178/178**; self-hosting fixpoint **OK**
(**3,032,308 bytes**; slice 10 was 3,027,925).

## What landed

`NkImport` nodes.  `Import` builds a node whose child 0 is the
`FROM` module (`NkIdent`) and whose following children are the imported
names; a plain `IMPORT` collects the module names as children.
`ImpList`/`ImpName`/`ImpModList` take the node as a parameter and append
to it.  The module-level `astImp`/`astImpTail` accumulator collects the
imports of a unit; each `NkUnit` stores them as **child 3**.

`AST.IsLeafKind` no longer lists `NkImport`, so a tree walk recurses into
its `NkIdent` children instead of mis-reading child 0 as a text index.

## Verified (temporary `AST.Dump`, then removed)

```modula2
FROM TestIO IMPORT WriteString, WriteLn;
```

gave `NkUnit(impdump, decls, body, imports=NkDeclSeq[
  NkImport(NkIdent TestIO, NkIdent WriteString, NkIdent WriteLn) ])`.

## Deliberately deferred

- `CLASS` / `CLASS IMPLEMENTATION` items and nested modules in the unit
  AST.
- `Lower` + `.ssa` byte-compare.
- The `MaxChild` cap still applies to `CASE` arms, `WITH` designators and
  call actuals.

## Next

`CLASS`/nested modules (or move to `Lower`).