mix-compression

# Mix Output Compression Mix commands (`mix test`, `mix credo`, `mix dialyzer`, `mix compile`) emit verbose, repetitive output that consumes context fast. This skill installs [rtk](https://github.com/rtk-ai/rtk) — a CLI proxy that filters tool output **before it lands in the transcript**. The filters short-circuit happy paths to a single line (`mix test: all pass`) while preserving full failure blocks, compile errors, and stack traces. Net win: 5-15% per-session token reduction on mix-heavy workflows. ## When to use - **Long sessions** — `/phx:work` or `/phx:full` hitting context limits from mix output - **Debugging loops** — `/phx:investigate` retrying `mix compile`/`mix test` repeatedly - **Dialyzer-heavy projects** — `mix dialyzer` output dominates the transcript ## Iron Laws 1. **NEVER strip critical signals** — compile errors (`** (CompileError)`, `== Compilation error in`), test failures (`FAILURES`, `0 failures` — preserved even on short-circuit), dialyzer warnings, and stack traces with `file:line` MUST pass through unchanged 2. **Verify after install** — run `rtk verify` (or `rtk verify --filter mix-test`) to confirm the bundled test fixtures pass before declaring success 3. **Never overwrite existing `.rtk/filters.toml`** — diff and merge instead ## Workflow ### Step 1: Detect rtk ```bash which rtk && rtk --version ``` Read `${CLAUDE_SKILL_DIR}/references/install.md` if rtk is missing — covers homebrew install + shell hook setup. ### Step 2: S...