Upgrade to Erlang/OTP 29 and Elixir 1.20.0

Bump the pinned toolchain in mise.toml and keep the Dockerfile in sync
(ELIXIR_VERSION, OTP_VERSION, and the Debian base required by the new
hexpm/elixir builder image). Keep Elixir OTP-tagged so the version-drift
check can parse the OTP major.

Author: andreogle

Dockerfile

@@ -12,9 +12,9 @@
 # binary from the official Node image — no npm/build toolchain ships
 # in the final image.
 
-ARG ELIXIR_VERSION=1.19.5
-ARG OTP_VERSION=28.5
-ARG DEBIAN_VERSION=trixie-20260421-slim
+ARG ELIXIR_VERSION=1.20.0
+ARG OTP_VERSION=29.0.1
+ARG DEBIAN_VERSION=trixie-20260518-slim
 ARG NODE_VERSION=26.2.0
 
 ARG BUILDER_IMAGE="hexpm/elixir:${ELIXIR_VERSION}-erlang-${OTP_VERSION}-debian-${DEBIAN_VERSION}"

mise.toml

@@ -3,8 +3,8 @@
 # into the repo; run `mise install` to fetch them. Pinning here keeps
 # every developer (and CI) on identical versions.
 [tools]
-erlang = "28.5"
+erlang = "29"
 # OTP-tagged so the precompiled Elixir build is guaranteed to match the
-# Erlang/OTP 28 above.
-elixir = "1.19.5-otp-28"
+# Erlang/OTP 29 above.
+elixir = "1.20.0-otp-29"
 node = "26"