M0: scaffold bnstoolkit mod (NeoForge 1.21.1)

Empty mod that loads cleanly on client + dedicated server. Sets up the
package layout and milestone TODOs for the BNS in-game UI work.

- uk.sijbers.bnstoolkit.{BnsToolkit, BnsToolkitClient} mod entries
- 5 placeholder screens extending a shared BaseBnsScreen
  (TierUpgrade, BountyBoard, QuestLog, PlotPurchase, ShopBrowser)
- 3 key bindings (T/B/P) registered, handlers TODO M1+
- SpurHud overlay placeholder for M4
- Network: payload registrar + one smoke-test C2S/S2C pair
  (RequestTierState / TierStateUpdate)
- en_us.json for screen + keybind labels
- neoforge.mods.toml pinned to neo_version 21.1.228 (live server match)

Build verified: ./gradlew build -> bnstoolkit-0.1.0.jar (15.6 KB).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -0,0 +1,61 @@
+# bnstoolkit
+
+Companion mod for the Brass and Sigil modpack. NeoForge 1.21.1.
+
+Provides the in-game UI surface for the KubeJS-driven civic tier, bounty,
+plot, and shop systems. Pure client visuals + a thin C2S/S2C network
+bridge over the existing server-side state — no server-side gameplay
+logic lives here, just transport and presentation.
+
+## Status
+
+M0 — scaffold only. Loads cleanly on client and dedicated server. No
+screens are open-able yet (key bindings register but their handlers are
+TODO). One network round-trip pair is wired as a smoke test.
+
+See `docs/bnstoolkit-architecture.md` in the brass-and-sigil repo for
+the full spec.
+
+## Building
+
+```
+./gradlew build
+```
+
+The output jar lands in `build/libs/bnstoolkit-<version>.jar`. Drop it
+into the modpack's `pack/overrides/mods/` directory.
+
+## Package layout
+
+```
+uk.sijbers.bnstoolkit
+├── BnsToolkit                   # common mod entry
+├── BnsToolkitClient             # client mod entry
+├── client
+│   ├── BnsKeyBindings           # T / B / P defaults
+│   ├── hud
+│   │   └── SpurHud              # spurs + tier overlay
+│   └── screens
+│       ├── BaseBnsScreen        # shared parent (will swap to FTB Library)
+│       ├── TierUpgradeScreen
+│       ├── BountyBoardScreen
+│       ├── QuestLogScreen
+│       ├── PlotPurchaseScreen
+│       └── ShopBrowserScreen
+└── network
+    ├── BnsNetwork               # payload registrar
+    ├── c2s
+    │   └── RequestTierStatePacket
+    └── s2c
+        └── TierStateUpdatePacket
+```
+
+## Milestones
+
+| Milestone | Scope |
+|---|---|
+| M0 (now) | Scaffold, keybinds, network smoke-test packet pair |
+| M1 | Tier upgrade screen + KubeJS bridge for tier/balance |
+| M2 | Quest log + shop browser screens |
+| M3 | Bounty board + plot purchase screens |
+| M4 | HUD overlay, mod settings screen, FTB Library swap |