Publish harness and TUI open-source

initial sync from the monorepo

crates/codegen/xai-grok-markdown/fuzz/README.md

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+# Fuzzing xai-grok-markdown
+
+Coverage-guided fuzzing for the markdown renderer using [cargo-fuzz](https://rust-fuzz.github.io/book/cargo-fuzz.html) (libFuzzer).
+
+## Prerequisites
+
+```bash
+cargo install cargo-fuzz   # if not already installed
+rustup toolchain install nightly
+```
+
+## Targets
+
+| Target | What it fuzzes |
+|---|---|
+| `render_all` | All 8 combos: `pretty × syntect × {full, streaming}` for every input |
+
+Each iteration runs:
+- `render_markdown_ratatui_full()` — 4 combos (pretty/non-pretty × syntect/no-syntect)
+- `StreamingMarkdownRenderer` char-by-char — same 4 combos
+
+## Running
+
+From `crates/codegen/xai-grok-markdown`:
+
+```bash
+# Run indefinitely (Ctrl-C to stop):
+cargo +nightly fuzz run render_all fuzz/corpus/render_all fuzz/seeds/render_all -- -max_len=16384
+
+# Run for 5 minutes:
+cargo +nightly fuzz run render_all fuzz/corpus/render_all fuzz/seeds/render_all -- -max_len=16384 -max_total_time=300
+```
+
+- `corpus/` — auto-generated inputs (gitignored)
+- `seeds/` — hand-written seed inputs (checked in)
+
+## Reproducing a crash
+
+When a crash is found, the input is saved to `artifacts/render_all/crash-<hash>`. Reproduce it with:
+
+```bash
+cargo +nightly fuzz run render_all fuzz/artifacts/render_all/crash-<hash>
+```
+
+## Adding seed inputs
+
+Drop `.txt` or `.md` files into `seeds/render_all/`. Good seeds cover distinct markdown features (tables, code blocks, emoji, nested lists, etc.) and help the fuzzer reach new code paths faster.