feat: v4.1.0 -- workshop-ready (logo, path discovery, docs)

Players install from Steam Workshop instead of install.sh, which failed on
Windows (bash) and a Manjaro box (hard-coded Mods globs). Adds Logo +
logo.png the uploader ships, tools/steam_paths.py reading Steam's
libraryfolders.vdf (Flatpak/Snap/second disk/Windows), and README install
tiers plus in-game publishing steps.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014TkQMhvEyoFqKzeCC69N6o

README.md

@@ -96,26 +96,70 @@ No stat or number is changed. Only *when* radiators run.
 
 ```
 mod.rules                              manifest + patch actions
+logo.png                               Workshop preview / in-game mod logo
 components/radiator_auto.rules         measures network headroom, gates the radiator
 tests/                                 offline validation suite
+tools/steam_paths.py                   finds the game and the Mods folder via Steam's library list
 tools/dotnet_enum.py                   reads component schemas out of Cosmoteer.dll
 tools/ildump.py                        disassembles component methods to readable CIL
-install.sh                             validate + copy into the Mods folder
+install.sh                             author's dev loop: validate + copy into the Mods folder
 ```
 
 ## Install
 
+### Steam Workshop (any OS)
+
+Subscribe to **Auto Radiator** on the Steam Workshop and enable it in the
+game's Mods menu. Steam places it under
+`steamapps/workshop/content/799600/<item id>/` and the game loads it from
+there; no files to copy.
+
+*Workshop link: pending first upload.*
+
+### Manual (any OS)
+
+Copy `mod.rules`, `logo.png` and the `components/` folder into a folder named
+`auto_radiator` inside your user Mods folder, then enable it in the Mods menu:
+
+| | Mods folder |
+|---|---|
+| Windows | `%USERPROFILE%\Saved Games\Cosmoteer\<SteamID>\Mods\` |
+| Linux (Proton) | `<Steam library>/steamapps/compatdata/799600/pfx/drive_c/users/steamuser/Saved Games/Cosmoteer/<SteamID>/Mods/` |
+
+### From this repo (Linux, for development)
+
 ```sh
 ./install.sh
 ```
 
-Then enable **Auto Radiator** in the game's Mods menu. `./install.sh --uninstall`
-removes it. If the script cannot find your Mods folder, set `COSMOTEER_MODS_DIR`.
+Validates against the installed game first, then copies the same file set the
+Workshop uploader ships. `./install.sh --uninstall` removes it. Discovery reads
+Steam's `libraryfolders.vdf`, so a second disk, Flatpak, Snap or the Debian
+package all work; if it still cannot find your Mods folder, set
+`COSMOTEER_MODS_DIR` (and `COSMOTEER_DATA` for the game data).
+
+## Publishing to the Workshop
+
+The uploader is built into the game; no `steamcmd` needed.
+
+1. `./install.sh` so the current files sit in the user Mods folder.
+2. In game: **Mods** → find *Auto Radiator* under *User Mods* → right-click →
+   **Upload to Steam Workshop**.
+3. Fill name, description, preview image (defaults to `logo.png`), visibility
+   and game version range → **Start Upload**.
+4. Updates use the same menu item; it asks for change notes. Bump `Version`
+   in `mod.rules` first — multiplayer and save syncing match on it.
+
+The **entire** mod folder is uploaded, which is why `install.sh` copies only
+`mod.rules`, `logo.png` and `components/`. The Workshop item is bound to the
+mod `ID`; keep `ganter.auto_radiator` stable. Steam does not refresh the
+preview image on later uploads, and rejects previews over 500 KB.
 
 ## Tests
 
 ```sh
-python3 tests/test_mod.py
+python3 tests/test_mod.py          # mod against installed game data
+python3 tests/test_steam_paths.py  # Steam library discovery, on fake layouts
 ```
 
 Cosmoteer applies mod actions to vanilla data at load time. Some mistakes crash
@@ -127,7 +171,8 @@ silently do nothing; see **Status** below for the four this project hit and the
 guard for each. The suite also self-checks its own parser against known vanilla
 facts first, so a broken parser fails loudly instead of passing everything.
 
-Set `COSMOTEER_DATA` to point at a different install, and `COSMOTEER_ASSEMBLY`
+The game is found through Steam's library list (`tools/steam_paths.py`). Set
+`COSMOTEER_DATA` to point at a different install, and `COSMOTEER_ASSEMBLY`
 for the schema checks.
 
 ## How to tell it is working