docs(work): map testing and editor northstars

Add repo-local northstars and ready slices for testing strategy, LSP/editor completion, and hemplate highlighting boundaries.

work/slices/SLICE-0010-highlight-boundary.md

@@ -0,0 +1,39 @@
+---
+id: SLICE-0010
+type: slice
+status: ready
+parent: NS-0003
+title: Define repo-owned hemplate highlighting boundary
+refs:
+  - docs/editor-support.md
+  - docs/hemplate-syntax.md
+  - REQUIREMENTS.md
+---
+
+## Objective
+
+Turn "tree-sitter highlighting for hemplate" into a bounded repo-owned contract: HTML stays the base grammar, hemplate overlay tokens are documented, and validation remains with `hemx-build`/`hemx-lsp`.
+
+## Authority
+
+`docs/editor-support.md` says normal HTML/tree-sitter tooling remains in use; `docs/hemplate-syntax.md` names the small overlay; `REQUIREMENTS.md` forbids a second template language or custom editor framework.
+
+## Close when
+
+- A highlighting boundary doc or work artifact lists the token classes the repo owns: escaped/trusted text delimiters, dynamic attribute prefix, `h-*` directives, and `data-hemx-*` facts.
+- It explicitly excludes diagnostics, completion, hover, formatting, Rust expression parsing, and build validation from highlighting authority.
+- It names what can be tested in-repo without editor package publishing.
+
+## Verification
+
+- `work check` for the slice contract now.
+- Later implementation: a repo-owned fixture/query test command, or a manual editor smoke if no automated query runner exists yet.
+
+## Non-goals
+
+- Do not introduce a new parser for `hemx-build`.
+- Do not publish or install editor packages.
+
+## Evidence
+
+The docs already establish `.heml` as HTML plus a small overlay; this slice makes that boundary executable before writing queries.