Update CHANGELOG and README for upcoming release

Add radio, checkbox collections, unique DOM ids, select improvements,
and preview server to unreleased changelog. Update README field guide
with unique id examples and label association patterns.

Author: bradgessler

CHANGELOG.md

@@ -1,5 +1,16 @@
 ## [Unreleased]
 
+### Added
+
+- **Radio component** with `field(:gender).radio("male")` API. Automatically handles name, value, and checked state. Each radio gets a unique DOM id based on its value (e.g. `user_gender_male`).
+- **Checkbox collection support** — three modes:
+  - **Boolean** (on/off toggle): `Field(:featured).checkbox` renders with hidden "0" input
+  - **All-options** (pick from known set): `Field(:role_ids).checkbox(value: role.id)` with `[]` name and unique ids per value
+  - **Field collection** (from existing array): `field(:role_ids).collection { |r| r.checkbox }` for values already on the model
+- **Unique DOM ids** for radio and checkbox groups via `DOM#id(*suffixes)`. Prevents duplicate ids in valid HTML and allows labels to target individual inputs.
+- **Select improvements**: blank options (`nil`) at any position, `multiple: true` support with hidden input for empty submissions, ActiveRecord relations as options.
+- **Preview server** — run `bin/preview` to view example forms at localhost:3000 with hot-reloading.
+
 ### Changed
 
 - **Deprecation**: Components now accept HTML attributes as keyword arguments directly instead of wrapping them in `attributes:`. The old `attributes:` keyword still works but emits a deprecation warning and will be removed in a future version.
@@ -32,6 +43,8 @@
   end
   ```
 
+- Required Ruby version bumped to 2.7.0.
+
 ## [0.6.1] - 2025-08-28
 
 ### Breaking Changes

README.md

@@ -407,11 +407,12 @@ class SignupForm < Components::Form
     end
 
     # Checkbox groups: loop over all possible options. Superform handles
-    # the name (with []), value, and checked state. You control the HTML.
+    # the name (with []), value, checked state, and unique ids. Each
+    # checkbox gets an id like "role_ids_1", "role_ids_2", etc.
     fieldset do
       legend { "Roles" }
       Role.all.each do |role|
-        label do
+        label(for: "#{field(:role_ids).dom.id}_#{role.id}") do
           Field(:role_ids).checkbox(value: role.id)
           whitespace
           plain role.name
@@ -420,11 +421,12 @@ class SignupForm < Components::Form
     end
 
     # Radio groups: iterate your options and call radio(value) on the field.
-    # Superform handles the name, value, and checked state automatically.
+    # Superform handles the name, value, checked state, and unique ids automatically.
+    # Each radio gets an id like "plan_id_1", "plan_id_2", etc.
     fieldset do
       legend { "Plan" }
       Plan.all.each do |plan|
-        label do
+        label(for: "#{field(:plan_id).dom.id}_#{plan.id}") do
           Field(:plan_id).radio(plan.id)
           whitespace
           plain plan.name