chore: replace em dashes with hyphens, add no-em-dash rule to CLAUDE.md

CLAUDE.md

@@ -6,18 +6,18 @@ tracking `main`, search indexed at build time by
 `@easyops-cn/docusaurus-search-local` so nothing external is keyed or called.
 
 Extracted from the `vantage` monorepo with its history, where it was
-`docsite/`. The whole repository is the site — there is no subdirectory.
+`docsite/`. The whole repository is the site - there is no subdirectory.
 
 It documents the **product**, not the codebase: each repository's own CLAUDE.md
 remains the contributor's map, and the two are allowed to differ in altitude but
-not in fact. Five sections — Getting started, Vantage, Vantage HQ, Reference,
-Operations — with `sidebars.ts` authored by hand so ordering is a decision
+not in fact. Five sections - Getting started, Vantage, Vantage HQ, Reference,
+Operations - with `sidebars.ts` authored by hand so ordering is a decision
 rather than a filename accident.
 
 ## A path, not a subdomain
 
 `*.vantage.hostxtra.co.uk` is the per-tenant instance namespace, and the control
-plane's `APP_ROOT_LABEL` resolves an instance from the label before `vantage` —
+plane's `APP_ROOT_LABEL` resolves an instance from the label before `vantage` -
 so a `docs.` label would be read as a tenant slug. Hence `/docs` on the
 marketing host instead.
 
@@ -25,7 +25,7 @@ marketing host instead.
 asset 404s:**
 
 1. `DOCS_BASE_URL` (default `/docs/` in the Dockerfile)
-2. the proxy location that routes here — which must also sort **above** the
+2. the proxy location that routes here - which must also sort **above** the
    catch-all forwarding to `site:3003`, or Next answers the 404 first
 3. the directory the runtime stage serves from,
    `/usr/share/nginx/html/docs`
@@ -39,7 +39,7 @@ Unlike the three Next apps this builds to static files, so its runtime stage is
 ## Design tokens
 
 `src/css/custom.css` holds `vantage-site`'s `web/app/globals.css` token blocks
-**copied verbatim** — same names, same values. This is the one place the tokens
+**copied verbatim** - same names, same values. This is the one place the tokens
 are not consumed through Tailwind: everything below the token block maps
 Docusaurus's `--ifm-*` variables onto them. Docusaurus already stamps
 `data-theme` on `<html>`, which is the selector the dark block keys on, so the
@@ -47,7 +47,7 @@ built-in toggle needed no wiring.
 
 The rule holds all the same: **no rule in that file outside the token blocks may
 carry a hex.** The one concession is `static/img/favicon.svg`, which must, for
-the same reason the email layout must — a browser tab cannot read a token.
+the same reason the email layout must - a browser tab cannot read a token.
 
 **Nothing enforces the match across the four front ends, and they are now in
 four repositories.** A token change here follows one in `vantage-site`; there is
@@ -71,13 +71,13 @@ Not part of a self-hosted install.
 ## CI/CD
 
 `.gitea/workflows/deploy.yml`, on every push to `main` plus `workflow_dispatch`.
-One image, `vantage/vantage-docs:latest`, from the repository root — the whole
+One image, `vantage/vantage-docs:latest`, from the repository root - the whole
 repository is the site, so there is nothing to detect a change in and it
 rebuilds on every push.
 
 **No build args are passed, deliberately.** `DOCS_URL`, `DOCS_BASE_URL`,
 `APP_URL` and `HQ_URL` all have correct defaults in the Dockerfile, and passing
-an unset repo variable would blank one rather than leave it alone — which for
+an unset repo variable would blank one rather than leave it alone - which for
 `DOCS_BASE_URL` means every asset path in the build. Change them in the
 Dockerfile. The monorepo's workflow passed none either; this preserves that.
 
@@ -88,3 +88,7 @@ Dockerfile. The monorepo's workflow passed none either; this preserves that.
 | `DOCKER_HOST`   | Variable | registry host used for image tags                         |
 
 Despite the name the workflow **does not deploy**; it only builds and pushes.
+
+## Writing style
+
+Never use em dashes (the long dash character) anywhere: code, comments, UI copy, docs, commit messages. Use a plain hyphen ` - `, a comma, a colon, or split the sentence instead.