initial commit: reforgermods.net launcher 0.1.0

A desktop server browser for Arma Reforger, built on the reforgermods.net v2
API. Live server list with search, sort and filters; a detail inspector with
population history and mod readiness; measured ICMP latency; favorites, recents
and settings; and direct joining through Steam.

Tauri 2 and Rust, with a Preact frontend that builds to 80 KB of JavaScript in
one chunk. Logic lives in rfm-core, which has no Tauri dependency and is tested
directly; src-tauri is the window, the command surface and the wiring.

Packaged for the public beta: a per-user NSIS installer, a portable .exe and an
Arch package, with signature-verified background updates on Windows and a
release pipeline that builds from a tag. The artifacts are not yet
Authenticode-signed — that is wired and waiting on an Azure Trusted Signing
identity, and docs/distribution.md says so plainly rather than letting anyone
discover it at the SmartScreen dialog.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/discord-presence.md

@@ -0,0 +1,84 @@
+# Discord Rich Presence — setup
+
+**Status: live.** Application id `1552757014474784898` is set in
+`src-tauri/src/presence.rs`.
+
+The launcher appears on a user's Discord profile the way DZSA Launcher does for
+DayZ — "Playing reforgermods.net launcher", with artwork, the server being
+viewed, and a button linking to the site.
+
+The application id supplies the *name* Discord displays, so the Discord
+application must be named exactly `reforgermods.net launcher`. Artwork still has
+to be uploaded for the large image to appear; see step 3.
+
+## What it looks like
+
+```text
+  ┌────┐  reforgermods.net launcher
+  │ RM │  Viewing [OGR2] Old Guard Revival 2
+  └────┘  12/128 players
+          [ Get the launcher ]
+```
+
+- **Application name** — from the Discord application. This is the headline and
+  the reason the application must be created with exactly the right name.
+- **Details / state** — from `rfm_core::presence`.
+- **Large image** — the asset keyed `logo` in the application's Rich Presence art.
+- **Button** — "Get the launcher" → `https://reforgermods.net`.
+
+## Remaining setup
+
+1. ~~Create the application~~ — done, id `1552757014474784898`.
+2. **Confirm the application name is exactly `reforgermods.net launcher`.** This
+   string is what every user's friends list shows; it cannot be changed
+   per-client, and it is the whole promotional value of the feature.
+3. **Upload the artwork.** Under **Rich Presence → Art Assets**, add
+   `brand/reforger-mods-app-icon.png` with the key **`logo`**, matching
+   `LARGE_IMAGE_KEY` in `src-tauri/src/presence.rs`. Until this exists the text
+   and button still show, but the card has no image.
+
+The application id is a public identifier, not a secret — it ships in every
+Discord game integration and is visible in any client's traffic. It is safe in
+the repository. Do **not** put the application's *client secret* or bot token
+anywhere near this project; Rich Presence needs neither.
+
+### Trying it without editing the source
+
+```sh
+RFM_DISCORD_APP_ID=123456789012345678 ./reforgermods-launcher
+```
+
+## Behaviour
+
+| Situation | Result |
+| --- | --- |
+| No application id configured | Presence is disabled; no thread, no socket. |
+| Discord not running | Connection fails quietly, retried at most every 30s. |
+| Discord restarts | Next update reconnects and republishes the current state. |
+| User turns it off in Settings | Presence is cleared immediately. |
+
+Presence runs on its own thread and is never awaited from a command, so Discord
+being slow, absent or broken cannot stall the UI.
+
+## Privacy
+
+Presence is **on by default**, since being visible is the point, but it is a
+visible toggle in Settings because it broadcasts the name of the server being
+viewed to the user's Discord friends. Nothing else is published: no account, no
+install identifier, no IP, no mod list.
+
+## Why the text rules are tested
+
+`crates/rfm-core/src/presence.rs` builds the strings and is unit tested, because
+server names are untrusted text from the API and Discord is unforgiving:
+
+- `details` and `state` cap at 128 characters, and Discord **silently drops** a
+  field under two characters rather than reporting an error.
+- Truncation is by character. Cutting a multi-byte glyph in half yields invalid
+  UTF-8 and Discord rejects the entire payload — so a server named in Japanese
+  or full of flag emoji would blank the presence rather than shorten it.
+- Control characters are stripped and whitespace collapsed, so a server name
+  containing newlines cannot reformat the presence card.
+
+The "reforgermods.net launcher" line is ours and is never taken from remote
+data, so a server cannot name itself something that impersonates the launcher.