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/EXISTING_REPO_CHECKLIST.md

@@ -1,63 +1,66 @@
-# Existing Repo Checklist
+---
+title: Existing Repo Checklist
+last_modified: 2026-02-22
+---
 
 Use this checklist when beginning work in a repo that may not yet conform to our
-[repository policies](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/REPO_POLICIES.md).
+repository policies
+(`https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/REPO_POLICIES.md`).
 
 Work on a feature branch. Check each item and fix any gaps before proceeding
 with your task.
 
-## Formatting (do this first)
+# Formatting (do this first)
 
 - [ ] If the repo has never been formatted to our standards, run `make fmt` and
       commit the result as a standalone branch/commit/PR before any other
       changes. Formatting diffs can be large and should not be mixed with
       functional changes.
 
-## Required Files
+# Required Files
 
 - [ ] `README.md` exists with all required sections (Description, Getting
       Started, Rationale, Design, TODO, License, Author)
 - [ ] `LICENSE` file exists and matches the README
-- [ ] `REPO_POLICIES.md` exists and version date is current with the
-      [authoritative source](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/REPO_POLICIES.md)
+- [ ] `REPO_POLICIES.md` exists and version date is current — fetch from
+      `https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/REPO_POLICIES.md`
 - [ ] `.gitignore` is comprehensive (OS, editor, language artifacts, secrets) —
       fetch from `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitignore`
       if missing
-- [ ] [`.editorconfig`](https://git.eeqj.de/sneak/prompts/raw/branch/main/.editorconfig)
-      exists
+- [ ] `.editorconfig` exists — fetch from
+      `https://git.eeqj.de/sneak/prompts/raw/branch/main/.editorconfig`
 - [ ] `Dockerfile` and `.dockerignore` exist; Dockerfile runs `make check` as a
       build step
 - [ ] Gitea Actions workflow in `.gitea/workflows/` runs `docker build .` on
       push — reference
-      [check.yml](https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitea/workflows/check.yml)
+      `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitea/workflows/check.yml`
 - [ ] Language-specific config:
-    - [ ] Go: `go.mod`, `go.sum`,
-          [`.golangci.yml`](https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml)
-    - [ ] JS: `package.json`, `yarn.lock`,
-          [`.prettierrc`](https://git.eeqj.de/sneak/prompts/raw/branch/main/.prettierrc),
-          [`.prettierignore`](https://git.eeqj.de/sneak/prompts/raw/branch/main/.prettierignore)
+    - [ ] Go: `go.mod`, `go.sum`, `.golangci.yml` (fetch from
+          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`)
+    - [ ] JS: `package.json`, `yarn.lock`, `.prettierrc`, `.prettierignore`
+          (fetch from
+          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.prettierrc` and
+          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.prettierignore`)
     - [ ] Python: `pyproject.toml`
-    - [ ] Docs/writing:
-          [`.prettierrc`](https://git.eeqj.de/sneak/prompts/raw/branch/main/.prettierrc),
-          [`.prettierignore`](https://git.eeqj.de/sneak/prompts/raw/branch/main/.prettierignore)
+    - [ ] Docs/writing: `.prettierrc`, `.prettierignore` (same URLs as above)
 
-## Makefile
+# Makefile
 
-- [ ] `Makefile` exists in root — reference the
-      [model Makefile](https://git.eeqj.de/sneak/prompts/raw/branch/main/Makefile)
+- [ ] `Makefile` exists in root — reference
+      `https://git.eeqj.de/sneak/prompts/raw/branch/main/Makefile`
 - [ ] Has targets: `test`, `lint`, `fmt`, `fmt-check`, `check`, `docker`,
       `hooks`
 - [ ] `make check` does not modify any files in the repo
 - [ ] `make test` has a 30-second timeout
 - [ ] `make check` passes on current branch
 
-## Formatting
+# Formatting
 
 - [ ] Platform-standard formatter is configured (`black`, `prettier`, `go fmt`)
 - [ ] Default formatter config, only exception: four-space indents (except Go)
 - [ ] All files pass `make fmt-check`
 
-## Git Hygiene
+# Git Hygiene
 
 - [ ] Pre-commit hook is installed (`make hooks`)
 - [ ] No secrets in the repo (`.env`, keys, credentials)
@@ -65,14 +68,14 @@ with your task.
       pinned by cryptographic hash with version/date comment
 - [ ] Using `yarn`, not `npm` (JS projects)
 
-## Directory Structure
+# Directory Structure
 
 - [ ] No unnecessary files in repo root
 - [ ] Files organized into canonical subdirectories (`bin/`, `cmd/`, `docs/`,
       `internal/`, `static/`, etc.)
 - [ ] Go migrations in `internal/db/migrations/` and embedded in binary
 
-## Final
+# Final
 
 - [ ] `make check` passes
 - [ ] `docker build` succeeds