build(steam): the SDK zip IS the only download — ContentBuilder included, links recorded

The partner dashboard offers exactly one download because there is only one: the SDK zip
carries the runtime (steam_api64.dll) and the release tooling (sdk/tools/ContentBuilder
with steamcmd.exe for Windows and steamcmd.sh for Linux/macOS, plus the app_build and
depot_build VDF templates). Verified against the zip rather than assumed.

scripts/steam-sdk.sh gains --contentbuilder, opt-in because it is 27 MB of binaries that
only the uploading machine needs.

Distribution.md §2 now opens with that fact — there is no separate ContentBuilder
download to hunt for — plus a reference table of the pages that actually get used:
SteamPipe upload, DLC setup, BIsDlcInstalled, store artwork sizes, Coming Soon window,
the Wallet rule, recurring subs, partner support and Steamworks.NET.

Distribution.md

@@ -40,6 +40,28 @@ dotnet publish ytLive.csproj -c Release -r win-x64 --self-contained true \
 
 ## 2. Steamworks setup, once
 
+**The SDK zip is the only download.** It is ~24 MB and contains the runtime
+(`sdk/redistributable_bin/win64/steam_api64.dll`) *and* the release tooling
+(`sdk/tools/ContentBuilder/` → `steamcmd.exe` for Windows, `steamcmd.sh` for Linux/macOS, plus the
+`app_build_*.vdf` / `depot_build_*.vdf` templates). There is no separate "ContentBuilder download"
+on the partner dashboard — the dashboard's Downloads page only re-offers the SDK.
+
+**Reference links, so nobody hunts again:**
+
+| What | Where |
+|---|---|
+| SDK zip (sign in to partner first) | `partner.steamgames.com/downloads/steamworks_sdk.zip` |
+| Docs home | `partner.steamgames.com/doc/home` |
+| SteamPipe upload (steamcmd + VDF fields) | `partner.steamgames.com/doc/sdk/uploading` |
+| DLC configuration | `partner.steamgames.com/doc/store/application/dlc` |
+| `BIsDlcInstalled` | `partner.steamgames.com/doc/api/ISteamApps` |
+| Store artwork sizes | `partner.steamgames.com/doc/store/assets/standard` |
+| Coming Soon / 2-week public window | `partner.steamgames.com/doc/store/coming_soon` |
+| Wallet rule (in-app purchases) | `partner.steamgames.com/doc/features/microtransactions` |
+| Recurring subscriptions | `partner.steamgames.com/doc/store/pricing/subscriptions` |
+| Partner support | `help.steampowered.com/en/wizard/HelpWithPublishing` |
+| Steamworks.NET (managed wrapper) | `nuget.org/packages/Steamworks.NET` |
+
 1. **Steamworks account** → onboarding (NDA, identity, company details, tax interview, payout bank,
    then the **$100 Steam Direct fee** per app). The store page cannot be configured before the fee.
 2. **App IDs.** One **base app** (free) and one **DLC app** (the lifetime Pro). Note both numbers:
@@ -49,9 +71,10 @@ dotnet publish ytLive.csproj -c Release -r win-x64 --self-contained true \
 4. **Steamworks SDK.** `./scripts/steam-sdk.sh ~/Downloads/steamworks_sdk_165.zip` extracts
    `steam_api64.dll` from `sdk/redistributable_bin/win64/` into `steam/` (gitignored) and stages
    `steam_appid.txt` = 480 — Valve's Spacewar app, so `SteamAPI.Init()` works locally before
-   LlamaCasty has an App ID. The csproj copies the DLL **beside the exe** (`Link`) with
-   `ExcludeFromSingleFile`, and copies `steam_appid.txt` in Debug only — never into a depot. The
-   managed side is the `Steamworks.NET` package (`SteamApps.BIsDlcInstalled`).
+   LlamaCasty has an App ID. Add `--contentbuilder` on the machine that uploads a depot. The csproj
+   copies the DLL **beside the exe** (`Link`) with `ExcludeFromSingleFile`, and copies
+   `steam_appid.txt` in Debug only — never into a depot. The managed side is the `Steamworks.NET`
+   package (`SteamApps.BIsDlcInstalled`).
 5. **Store page** configured and made public **two weeks before release** — Valve's rule, and it is
    the window where wishlists accumulate.