Fix review issues: front matter, headings, consistency, typos

- Move title and last_modified to YAML front matter (all policy docs)
- Make all document sections H1, subsections H2
- Update version rule to reference front matter format
- Fix "our" → "your" typo in Go styleguide
- Fix Python styleguide numbering (2. → 1.)
- Fix README: "flat collection" → accurate description, remove stale TODO
- Remove Makefile items from code styleguides (repo stuff, not code),
  add note linking to Repository Policies
- Change zerolog → slog in Go styleguide
- Fix JS styleguide npm reference: both work, but use make targets
- Drop .json from healthcheck path, add JSON content-type requirement
- Add Author/License to Go HTTP Server Conventions
- Convert hyperlinks to backtick URLs in checklists for consistency
- Add version/front matter to both checklists

prompts/CODE_STYLEGUIDE_JS.md

@@ -1,6 +1,7 @@
-Version: 2026-02-22
-
-# JavaScript / ECMAScript / ES6
+---
+title: Code Styleguide — JavaScript
+last_modified: 2026-02-22
+---
 
 1. Use `const` for everything. If you need to reassign, use `let`. Never use
    `var`.
@@ -11,9 +12,12 @@ Version: 2026-02-22
 
 1. Use `prettier` for code formatting, with four spaces for indentation.
 
-1. At a minimum, `npm run test` and `npm run build` should work (complete the
-   appropriate scripts in `package.json`). The `Makefile` should call these, do
-   not duplicate the scripts in the `Makefile`.
+1. At a minimum, both `yarn run test`/`yarn run build` and
+   `npm run test`/`npm run build` should work (complete the appropriate scripts
+   in `package.json`). However, prefer `make test` and `make build` instead —
+   the Makefile is authoritative on how to interact with the repo. See
+   [Repository Policies](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/REPO_POLICIES.md)
+   for details.
 
 # Author