MdChat Markdown editor with Muse Spark

# MdChat

Native macOS Markdown previewer and vim-keyed editor, with a Gemini chat panel
that answers questions about whatever part of the document you pick — and can
rewrite it in place, behind a diff you approve.

## Requirements

- macOS 13 or newer
- Xcode command line tools, Swift 5.9+ — `xcode-select --install` if `swift
  --version` comes back empty
- An API key for at least one provider: Gemini or Meta Model API (Muse Spark)

No Xcode project and no SwiftPM dependencies. The only third-party code is
vendored JavaScript: markdown-it, Mermaid, and CodeMirror 5 with its vim keymap.

## Setup

```sh
git clone <your-remote> MdChat
cd MdChat
chmod +x fetch-deps.sh build.sh
./fetch-deps.sh          # downloads the pinned JS into Resources/vendor
./build.sh               # -> MdChat.app
open MdChat.app
```

`fetch-deps.sh` needs network access and only has to run once — but it is
required, because `vendor/` is gitignored and the app renders nothing without
it. `build.sh` takes `debug` or `release` (default `release`) and ad-hoc signs
the bundle so Keychain and network access behave.

The app icon comes from `Icon/AppIcon.icns`, which `build.sh` copies into the
bundle. To change the artwork, replace `Icon/icon-1024.png` and run
`./make-icon.sh` (which uses `sips` and `iconutil`).

Move `MdChat.app` wherever you like, or leave it in the tree. Rebuilding
replaces it, so keep it where `build.sh` puts it if you plan to iterate.

## Providers and API keys

Two backends, one conversation. Press **⌘,**, pick the provider tab, paste its
key, set a model ID, **Save**. The checkbox in that sheet is what makes a
provider active — saving a key doesn't switch to it, so you can keep both
configured and flip between them from the toolbar menu or the Chat menu.

| | Gemini | Muse Spark |
| --- | --- | --- |
| Key from | <https://aistudio.google.com/apikey> | Meta Model API (`MODEL_API_KEY`) |
| Endpoint | `streamGenerateContent?alt=sse` | `https://api.meta.ai/v1/chat/completions` |
| Auth header | `x-goog-api-key` | `Authorization: Bearer` |
| Default model | `gemini-3.8-flash` | `muse-spark-1.3-contributor` |

Keys go into your login Keychain under service `MdChat`, one account per
provider — never a file in the project or a plist. Nothing in the repo will ever
contain one. To check or remove them outside the app:

```sh
security find-generic-password -s MdChat -a gemini -w