Tier Chip SVG

Raw SVG fragment shown when the resource's SVG is rendered at <60px wide — favicon, tree node, breadcrumb dot. Placed inside the `<g class="tier-chip">` group. Supports placeholders `{{label}}`, `{{firstLetter}}`, `{{uri}}`, `{{resourceKey}}` (substituted per-instance; `{{resourceKey}}` is the URI's final segment — the YAML top-level key of the instance — useful for instance-driven classes whose key IS the canonical short code, e.g. environments, regions, status codes). CSS variables like `var(--kan-accent)` work directly inside the fragment.