Replace the protobuf hex package (agent.pb.ex) and hand-written validator
(validator.ex) with a pure Gleam implementation: wire format primitives,
all 23 message types, encode/decode functions, and validation merged into
decode. Thin Elixir wrappers in agent.ex preserve the existing struct API.
- Wire format: varint, length-delimited, double (IEEE 754 via FFI), tag encode/decode
- Types: all proto3 message types as Gleam custom types with enums and oneof
- Decode: field-level parsing with integrated validation (UUID, IP, hostname, limits)
- Encode: proto3 default omission, bytes_tree concatenation, map/repeated fields
- Wrappers: Elixir structs with encode/decode delegating to Gleam, enum atom conversion
- Remove {:protobuf, "~> 0.12"} dependency
Reviewed-on: graham/towerops-web#104
Migrate three pure-function modules from Elixir to Gleam:
- polling_offset: deterministic hash-based polling offset (pure Gleam, no FFI)
- changelog_parser: text parsing logic in Gleam, thin Elixir wrapper for File I/O
- user_agent_parser: regex-based UA parsing in Gleam with Erlang FFI for
atom-keyed map conversion
Add gleam_regexp dependency for regex support in Gleam modules.
Update all call sites and tests to use Gleam module atoms.
Reviewed-on: graham/towerops-web#103
Set up mix_gleam archive, gleam_stdlib, and gleeunit deps. Add Gleam
compiler to all Dockerfiles, CI workflows, nix shell, and .tool-versions.
Rewrite Numeric, QueryHelpers, and URLValidator from Elixir to Gleam with
full ExUnit test coverage. Update all callers to use the Gleam modules
directly via :towerops@module syntax. Remove duplicate sanitize_like/1
private functions in snmp.ex and trace.ex.
Reviewed-on: graham/towerops-web#98
