docs(ROADMAP): log P4 debt — surface int-literals host-narrowed at concept layer

ROADMAP.md

@@ -346,6 +346,7 @@ Per-row tagging is a scheduled follow-up sweep — **trigger:** post-merge of th
 ### P4 — type refinement / modeling faithfulness
 
 - **Fixed-width types aren't structurally fixed**: `dsl/std/bit.dag` uses nominal records with `List<Bit>` / `List<Byte>` fields — cardinality not substrate-enforced; alias-form refinements unavailable until alias `where` parses/lowers ([db-11 gap](docs/db-history/db-11.md)). Dissolution: wire type-alias refinement, field refinement, or a `Cardinality(element, Exact(n))`-style carrier.
+- **Surface int-literals are concept-layer host-narrowed, not reconciliation-narrowed**: `src/v3/std/tokenize.dag:30` declares `IntLit(Int)` where `Int = Int64 = OrderedRing<Word64>` (`dsl/std/integer.dag:43`), so the lexer's digit-run → token concept is already narrowed to host `i64` at the tokenizer boundary. Surfaced 2026-04-24 by substrate lane-owner analysis: `i64::MIN` as a single-token literal is unrepresentable (principled workaround `(0 - MAX - 1)` exists under `OrderedRing` additive-inverse — pure ring arithmetic over representable operands). The class generalizes to `UInt64` upper boundary `2^64 - 1` and to silent narrowing of typed numerics in non-`Int64` contexts. Dissolution: `IntLit` carries an unbounded magnitude at the concept layer (candidate carrier: a `std.natural` / magnitude-unbounded-natural type), narrows to the target int algebra at reconciliation; negation stays `OrderedRing` additive-inverse — no unary-minus parse primary is needed (`src/v3/compiler/parse_tables.dag:413-448` documents the closed-set prefix-opener dispatch with a full 4-pattern dissolution audit, and `-x = 0 - x` desugars principally under the ring). Adjacent to the fixed-width-types row above (shared DB-11 alias-`where` + cardinality-substrate blocker family) and to the Post-R1 Grounding Completeness Program (`ROADMAP.md:149` — surface-side sibling to that program's target-side primitive-grounding claim; natural fit as a Tier-1 thesis-claim vignette once the program opens). Owner: unassigned; M scope.
 
 ### Post-merge debt (2026-04-20 cleanup brief)