Add ADT variant codec docs and telemetry dep

Document a new ADT/Variant codec and telemetry support: update README with a Variant codec builder example and add entries to CHANGELOG describing variant codecs and telemetry events. Also add the telemetry dependency (>= 1.0.0 and < 2.0.0) to gleam.toml and manifest.toml (package entry and requirement).

Author: lupodevelop

CHANGELOG.md

@@ -8,6 +8,11 @@
   notifications for `NodeUp` and `NodeDown`.
 - `distribute.subscribe(subject)` — Start a monitored subscription.
 - `distribute.unsubscribe(monitor_subject)` — Stop a subscription.
+- **ADT/Variant Codecs** (`distribute/codec/variant`) — A builder pattern to
+  easily create codecs for Custom Types (enums) with payload support.
+- `variant.new()`, `variant.add()`, `variant.unit()`, `variant.build()`
+- **Telemetry** (`distribute/internal/telemetry`) — Erlang `:telemetry` events
+  for send, receive, encode, decode, registry, and cluster operations.
 
 ## v3.0.0 — 2026-02-11
 

README.md

@@ -122,12 +122,35 @@ the fields together!
 | `distribute/cluster` | `net_kernel` start/connect/ping |
 | `distribute/codec` | Binary codecs for primitives + `subject()` |
 | `distribute/codec/composite` | Option, Result, Tuple codecs |
+| `distribute/codec/variant` | Build codecs for Custom Types (ADTs) |
 | `distribute/codec/tagged` | Tagged messages with version field |
 | `distribute/global` | `GlobalSubject(msg)`, `call`, `reply` |
 | `distribute/cluster/monitor` | `NodeUp`, `NodeDown` typed events |
 | `distribute/registry` | `TypedName(msg)`, `:global` registration |
 | `distribute/receiver` | Typed receive, OTP actor wrappers |
 
+### Custom Type Codecs
+
+Seamlessly encode and decode your Algebraic Data Types (enums) with a fluent builder.
+
+```gleam
+pub type MyMessage {
+  Text(String)
+  Ping
+}
+
+import distribute/codec
+import distribute/codec/variant
+
+let my_codec = 
+  variant.new()
+  |> variant.add(0, "Text", codec.string(), Text, fn(m) {
+    case m { Text(s) -> Ok(s); _ -> Error(Nil) }
+  })
+  |> variant.unit(1, "Ping", Ping, fn(m) { m == Ping })
+  |> variant.build()
+```
+
 ### Cluster Monitoring
 
 Subscribe to cluster events (`NodeUp`, `NodeDown`) to react to node topology changes.

gleam.toml

@@ -13,6 +13,7 @@ target = "erlang"
 gleam_stdlib = ">= 0.60.0 and < 2.0.0"
 gleam_erlang = ">= 1.0.0 and < 2.0.0"
 gleam_otp = ">= 1.0.0 and < 2.0.0"
+telemetry = ">= 1.0.0 and < 2.0.0"
 
 [dev-dependencies]
 gleeunit = ">= 1.0.0 and < 2.0.0"

manifest.toml

@@ -6,10 +6,12 @@ packages = [
   { name = "gleam_otp", version = "1.2.0", build_tools = ["gleam"], requirements = ["gleam_erlang", "gleam_stdlib"], otp_app = "gleam_otp", source = "hex", outer_checksum = "BA6A294E295E428EC1562DC1C11EA7530DCB981E8359134BEABC8493B7B2258E" },
   { name = "gleam_stdlib", version = "0.68.1", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "F7FAEBD8EF260664E86A46C8DBA23508D1D11BB3BCC6EE1B89B3BC3E5C83FF1E" },
   { name = "gleeunit", version = "1.9.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleeunit", source = "hex", outer_checksum = "DA9553CE58B67924B3C631F96FE3370C49EB6D6DC6B384EC4862CC4AAA718F3C" },
+  { name = "telemetry", version = "1.3.0", build_tools = ["rebar3"], requirements = [], otp_app = "telemetry", source = "hex", outer_checksum = "7015FC8919DBE63764F4B4B87A95B7C0996BD539E0D499BE6EC9D7F3875B79E6" },
 ]
 
 [requirements]
 gleam_erlang = { version = ">= 1.0.0 and < 2.0.0" }
 gleam_otp = { version = ">= 1.0.0 and < 2.0.0" }
 gleam_stdlib = { version = ">= 0.60.0 and < 2.0.0" }
 gleeunit = { version = ">= 1.0.0 and < 2.0.0" }
+telemetry = { version = ">= 1.0.0 and < 2.0.0" }