haskell: Phase 9 conformance — partial.hs (7/7), Phase 9 complete

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plans/haskell-completeness.md

@@ -138,7 +138,7 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
   an `hk-error` whose message contains the given substring.
 - [x] Tests in `lib/haskell/tests/errors.sx` (≥ 10 tests: error message
   content, undefined, head/tail/fromJust on bad input, `hk-test-error` helper).
-- [ ] Conformance programs:
+- [x] Conformance programs:
   - `partial.hs` — exercises `head []`, `tail []`, `fromJust Nothing` caught
     at the top level; shows error messages.
 
@@ -293,6 +293,14 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 9 conformance: `partial.hs` (7/7) → Phase 9 complete:
+- New `tests/program-partial.sx` exercising `head []`, `tail []`,
+  `fromJust Nothing`, `undefined`, and user `error` from inside a `do` block;
+  verifies the error message lands in `hk-run-io`'s `io-lines`. Also a happy-
+  path test (`head [42] = 42`) and a "putStrLn before error preserves prior
+  output, never reaches subsequent action" test.
+- Added `partial` to `PROGRAMS` in `conformance.sh`. Phase 9 done.
+
 **2026-05-07** — Phase 9 `tests/errors.sx` (14/14):
 - New file with 14 tests covering: error w/ literal + computed message; error
   in `if` branch (laziness boundary); undefined via direct + forcing-via-