haskell: Phase 7 conformance — caesar.hs (+8 tests, 8/8)

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

plans/haskell-completeness.md

@@ -284,6 +284,15 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-06** — Phase 7 conformance (caesar.hs):
+- New `lib/haskell/tests/program-caesar.sx` (8 tests). Caesar cipher exercising
+  `chr`, `ord`, `isUpper`, `isLower`, `mod`, `map`, and `(x:xs)` pattern matching
+  over native String values via the Phase 7 string-view path. Adapted from
+  https://rosettacode.org/wiki/Caesar_cipher#Haskell.
+- `caesar` added to `PROGRAMS` in `lib/haskell/conformance.sh`. Suite isolated:
+  8/8 passing. Note: `else chr c` in `shift` keeps the char-as-string output type
+  consistent with the alpha branches (pattern bind on a string view yields an int).
+
 **2026-05-06** — Phase 7 complete (string-view O(1) head/tail + `++` native concat):
 - `runtime.sx`: added `hk-str?`, `hk-str-head`, `hk-str-tail`, `hk-str-null?`.
   String views are `{:hk-str buf :hk-off n}` dicts; native SX strings satisfy the