haskell: Phase 17 — import declarations anywhere among top-level decls

hk-collect-module-body previously ran a fixed import-loop at the start
and then a separate decl-loop; merged into a single hk-body-step
dispatcher that routes `import` to the imports list and everything else
to hk-parse-decl. Both call sites (initial step + post-semicolon loop)
use the dispatcher. The eval side reads imports as a list (not by AST
position) so mid-stream imports feed into hk-bind-decls! unchanged.

tests/parse-extras.sx 12 → 17: very-top, mid-stream, post-main,
two-imports-different-positions, unqualified-mid-file. Regression
sweep clean: eval 66/0, exceptions 14/0, typecheck 15/0, records 14/0,
ioref 13/0, map 26/0, set 17/0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plans/haskell-completeness.md

@@ -320,7 +320,7 @@ larger conformance programs and removes one-line workarounds in test sources.
   `return (42 :: Int)`. Parser currently rejects `::` in `aexp` position;
   desugar should drop the annotation (we have no inference at this layer
   yet, so it's a parse-only pass-through).
-- [ ] `import` declarations anywhere at the start of a module — currently
+- [x] `import` declarations anywhere at the start of a module — currently
   only the very-top-of-file form is recognised. Real test programs that
   mix prelude code with `import qualified Data.IORef` need this.
 - [ ] Multi-line top-level `where` blocks (`where { ... }` with explicit
@@ -420,6 +420,18 @@ constraints (qualified types `[ClassName var] => type`).
 
 _Newest first._
 
+**2026-05-10** — Phase 17 second box: `import` declarations anywhere among
+top-level decls. `hk-collect-module-body` previously ran a fixed
+import-loop at the start, then a separate decl-loop; merged into a single
+`hk-body-step` dispatcher that routes `import` to the imports list and
+everything else to `hk-parse-decl`. Each call site (initial step + post-
+semicolon loop) now uses the dispatcher. Imports collected mid-stream
+still feed into `hk-bind-decls!` correctly because the eval side reads
+them via the imports list, not by AST position. tests/parse-extras.sx
+12 → 17 covering very-top, mid-stream, post-main, two-imports-different-
+positions, and unqualified mid-file. Regression: eval 66/0, exceptions
+14/0, typecheck 15/0, records 14/0, ioref 13/0, map 26/0, set 17/0.
+
 **2026-05-08** — Phase 17 first box: expression type annotations `(x :: Int)`,
 `f (1 :: Int)`, `(\x -> x+1) :: Int -> Int`. Parser's `hk-parse-parens`
 gains a `::` arm after the first inner expression: consume `::`, parse a