Record grammar-only surface gaps

DECISIONS.md

@@ -36,3 +36,5 @@ against the existing examples.
 - **Stage-1 exception: the imported interpreter's header comment was corrected in place** (`tested: 18/18` → the provable `10 tests in js/test/`) — a falsified claim inside the canonical artifact outranks byte identity with the pre-Stage-1 deploy; end-state identity is restored when the site deploys the pinned file.
 - **Stage-3 ratification (2026-07-09): the 26 judgment calls are ruled; JUDGMENT_CALLS.md is the semantic record of MPL M0.** Per-ruling record: (1) ÷0 is `err_div0`; (2) a `∀` expression is always `⊥`; (3) an unmatched guard yields `⊥` unless caught by `|`; (4) numbers are exact rationals — BigInt num/den, lowest terms, den > 0, decimal literals exact, display `n` or `n/d` (re-evaluates to itself); IEEE doubles rejected; (5) `✎` rendering spec'd per type; (6) `⊥` is first-class, arithmetic on it `err_num`; (7) equality is structural on data, cross-type `=` false, `0.5 = 1/2` true, any function in `=`/`≠` raises `err_fn_eq`; (8) ordering is number×number and string×string (code-point) only, else `err_compare`; (9) closures capture the environment; (10) λ-application depth counter, limit 10000, `err_depth` — no keyless host error may remain reachable; (11) the 500000-step budget is an environment resource limit, not semantics — corpus entry 053 moved to js/test; (12) string escapes are exactly `\n \t \" \\`, anything else `err_escape` (grammar ESC amended to match); (13) guard conditions must be boolean, else `err_bool`; (14) `∧ ∨` short-circuit and demand booleans on evaluated operands (`err_bool`); (15) braces group, binders scope; (16) `≜` binds once per scope (`err_redef`; inner shadowing legal), `←` mutates an existing binding only (`err_unbound`); (17) type constraints parse, unenforced; (18) nullary `λ: e` admitted (grammar amended); (19) `∗` ≡ `×`; (20) the empty program is valid; (21) `( seqExpr )` — the interpreter now implements it; (22) `∘` is composition, `(f ∘ g)(x…) = f(g(x…))`, non-function operand `err_notfn`; (23) set literals parse, evaluate to `err_notyet`; (24) record literals likewise; (25) `λ(a, b):` rejected everywhere; (26) `λ` is reserved — never an identifier — while other Greek letters remain identifiers.
 - **Standing M1 decisions logged at ratification**: `√` vs ℚ (irrationals); an explicit local-binding construct (let/where); set semantics; record semantics; comprehension notation; `‖` parallel semantics.
+- **Grammar-only surface gaps are on the record** (SURFACE.md "Grammar-only surface" section): `≈`/`∼` comparisons, `"""raw strings"""`, hex/binary/exponent literals, and `_` as a λ pattern all parse in the grammar and fail in the Stage-3 interpreter — Stage 4+ material, no ruling; `err_comment` is dead pending removal at the next legitimate interpreter change.
+- **Ruling 12's enumeration governs string escapes**: the grammar's ESC fragment was narrowed to exactly `\n \t \" \\` — `\r`, `\0` and `\u{hex}` were removed from the grammar; they were never in the ratified set.