docs: add session brief for expert agent work

Coverage status, priority work items, and file map for
guided Claude session on WASM size, benchmarks, and TS typedefs.

Co-Authored-By: Virgil <virgil@lethean.io>

SESSION-BRIEF.md

@@ -0,0 +1,79 @@
+# Session Brief: core/go-html
+
+**Repo**: `forge.lthn.ai/core/go-html` (clone at `/tmp/core-go-html`)
+**Module**: `forge.lthn.ai/core/go-html`
+**Status**: 19 Go files, 1,591 LOC, 53 tests ALL PASS
+**Wiki**: https://forge.lthn.ai/core/go-html/wiki (6 pages)
+
+## What This Is
+
+HLCRF DOM compositor with grammar pipeline. Renders semantic HTML from composable node trees with:
+- **Node interface**: El, Text, Raw, If, Unless, Each[T], Switch, Entitled
+- **HLCRF Layout**: Header/Left/Content/Right/Footer with ARIA roles
+- **Responsive**: Multi-variant breakpoint rendering
+- **Pipeline**: Render → strip tags → tokenise via go-i18n/reversal → GrammarImprint
+- **WASM target**: `cmd/wasm/` exposes renderToString() and registerComponents() to JS
+- **Codegen**: Web Component classes with closed Shadow DOM
+
+## Current State
+
+| Area | Status |
+|------|--------|
+| Core (node, layout, responsive, pipeline) | SOLID — all tested, clean API |
+| Tests | 53/53 pass, excellent coverage ratios |
+| go vet | Clean |
+| TODOs/FIXMEs | None |
+| WASM build | FAILS — 1.58 MB gzip exceeds 1 MB Makefile limit |
+| Codegen | Working — generates WC classes |
+
+## Dependencies
+
+- `forge.lthn.ai/core/go-i18n` (replace directive → `../go-i18n`)
+- `github.com/stretchr/testify` v1.11.1
+- `golang.org/x/text` v0.33.0
+
+## Priority Work
+
+### High (blockers)
+1. **Fix WASM size** — Move `buildComponentJS()` / JSON parsing to server-side. WASM should only do `Render()`. Current: 6.0 MB raw / 1.58 MB gzip.
+2. **WASM integration tests** — No `cmd/wasm/main_test.go` exists. Can't test JS↔Go round-trip.
+
+### Medium (completeness)
+3. **Performance benchmarks** — No `BenchmarkRender()` or `BenchmarkImprint()`. Add them.
+4. **TypeScript type definitions** — Codegen only produces JS. Add `.d.ts` generation for WC bundle.
+5. **Accessibility helpers** — Layout has semantic HTML + ARIA roles, but no aria-label builder or alt text helpers.
+6. **Layout variant validation** — `NewLayout("XYZ")` silently produces empty output. Could warn.
+
+### Low (hardening)
+7. **Unicode/RTL edge cases** — Test emoji, RTL text in Text nodes
+8. **Deep nesting stress test** — Circular or very deep Layout nesting
+9. **Large Each[T]** — Test with thousands of items
+10. **Browser polyfill docs** — Closed Shadow DOM support matrix
+
+## File Map
+
+```
+/tmp/core-go-html/
+├── node.go (254)        + node_test.go (206)
+├── layout.go (119)      + layout_test.go (116)
+├── pipeline.go (83)     + pipeline_test.go (128)
+├── responsive.go (39)   + responsive_test.go (89)
+├── context.go (27)
+├── render.go (9)        + render_test.go (97)
+├── path.go (22)         + path_test.go (86)
+├── integration_test.go (52)
+├── cmd/wasm/
+│   ├── main.go (78)     — WASM entry point
+│   ├── register.go (18) + register_test.go (24)
+├── codegen/
+│   ├── codegen.go (90)  + codegen_test.go (54)
+├── go.mod
+└── Makefile
+```
+
+## Conventions
+
+- UK English (colour, organisation)
+- `declare(strict_types=1)` equivalent: all types annotated
+- Tests: testify assert/require
+- Licence: EUPL-1.2