feat(metadata|docs): reusable tag groups with $group: (#5037)

* feat(metadata): reusable tag groups with `$group:`

A `$group:<group-name>` marker in `tags` is replaced in place with the tags of
`groups/<group-name>.json`: a small set of tags for what a variant suffix
means, such as `-minus` → remove, delete.

- Read groups in `readGroups` and resolve markers next to `$extends:`,
  failing on unknown groups and on `$group:` outside `tags`
- Add `group.schema.json` and lint, spell-check and format `groups/*.json`
- `pnpm checkIcons` also fails on literals a group already provides, and
  warns about icons that list a group's tags by hand and unused groups
- Add the `minus`, `plus` and `x` groups and use them in
  `alarm-clock-minus`, `file-minus`, `file-plus` and `file-x`

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Fix group checker

* Apply batched suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* feat(metadata): reusable tag groups with `$group:`

A `$group:<group-name>` marker in `tags` is replaced in place with the tags of
`groups/<group-name>.json`: a small set of tags for what a variant suffix
means, such as `-minus` → remove, delete.

- Read groups in `readGroups` and resolve markers next to `$extends:`,
  failing on unknown groups and on `$group:` outside `tags`
- Add `group.schema.json` and lint, spell-check and format `groups/*.json`
- `pnpm checkIcons` also fails on literals a group already provides, and
  warns about icons that list a group's tags by hand and unused groups
- Add the `minus`, `plus` and `x` groups and use them in
  `alarm-clock-minus`, `file-minus`, `file-plus` and `file-x`

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Fix group checker

* Apply batched suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* feat(metadata): reusable tag groups with `$group:`

A `$group:<group-name>` marker in `tags` is replaced in place with the tags of
`groups/<group-name>.json`: a small set of tags for what a variant suffix
means, such as `-minus` → remove, delete.

- Read groups in `readGroups` and resolve markers next to `$extends:`,
  failing on unknown groups and on `$group:` outside `tags`
- Add `group.schema.json` and lint, spell-check and format `groups/*.json`
- `pnpm checkIcons` also fails on literals a group already provides, and
  warns about icons that list a group's tags by hand and unused groups
- Add the `minus`, `plus` and `x` groups and use them in
  `alarm-clock-minus`, `file-minus`, `file-plus` and `file-x`

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Fix group checker

* Apply batched suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* feat(metadata): reusable tag groups with `$group:`

A `$group:<group-name>` marker in `tags` is replaced in place with the tags of
`groups/<group-name>.json`: a small set of tags for what a variant suffix
means, such as `-minus` → remove, delete.

- Read groups in `readGroups` and resolve markers next to `$extends:`,
  failing on unknown groups and on `$group:` outside `tags`
- Add `group.schema.json` and lint, spell-check and format `groups/*.json`
- `pnpm checkIcons` also fails on literals a group already provides, and
  warns about icons that list a group's tags by hand and unused groups
- Add the `minus`, `plus` and `x` groups and use them in
  `alarm-clock-minus`, `file-minus`, `file-plus` and `file-x`

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Fix group checker

* Apply batched suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

group.schema.json

@@ -0,0 +1,40 @@
+{
+  "$id": "https://lucide.dev/group.schema.json",
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$vocabulary": {
+    "https://json-schema.org/draft/2020-12/vocab/core": true,
+    "https://json-schema.org/draft/2020-12/vocab/applicator": true,
+    "https://json-schema.org/draft/2020-12/vocab/unevaluated": true,
+    "https://json-schema.org/draft/2020-12/vocab/validation": true,
+    "https://json-schema.org/draft/2020-12/vocab/meta-data": true,
+    "https://json-schema.org/draft/2020-12/vocab/format-annotation": true,
+    "https://json-schema.org/draft/2020-12/vocab/content": true
+  },
+  "title": "Lucide Icons group schema",
+  "type": "object",
+  "additionalProperties": false,
+  "required": ["$schema", "description", "tags"],
+  "properties": {
+    "$schema": {
+      "type": "string"
+    },
+    "description": {
+      "type": "string",
+      "minLength": 1,
+      "description": "One line describing which meaning this group covers."
+    },
+    "tags": {
+      "type": "array",
+      "items": {
+        "type": "string",
+        "minLength": 1,
+        "not": {
+          "pattern": "^\\$[a-zA-Z]"
+        }
+      },
+      "minItems": 1,
+      "uniqueItems": true
+    }
+  },
+  "description": "A JSON Schema for reusable groups defined by Lucide Icons."
+}