feat: otpiser Phase 1 — supervision tree codegen, Elixir module generation, tests

Generate complete Elixir OTP applications from manifest:
- Application, Supervisor, GenServer module templates
- mix.exs project file generation
- Three supervision strategies (one_for_one, one_for_all, rest_for_one)
- Nested supervisor tree support with child spec configurations
- Supervision tree ASCII diagram
- ExUnit test file generation
- Manifest extended with [[supervisors]] and [[supervisors.children]] tables
- 13 integration tests covering all strategies, restart types, and edge cases

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath