feat: add wasm-dot package for Polkadot transaction building and decoding

WASM-based Polkadot/Substrate transaction builder, parser, and explainer
for use by sdk-coin-dot (tdot). Supports transfers, staking operations,
proxy management, and batched calls.

Key capabilities:
- Build unsigned extrinsics from high-level intents (transfer, stake, batch, proxy)
- Parse signed/unsigned extrinsics with metadata-aware signed extension decoding
- Explain transactions: derive type, extract outputs/inputs, attach DOT-specific metadata
- Proxy type resolution from chain metadata (works across Polkadot, Kusama, Westend)
- parseTransaction returns DotTransaction with .parse() method (PSBT pattern)

BTC-0

Author: lcovar

package-lock.json

@@ -0,0 +1,11 @@
+target/
+node_modules/
+# we actually only track the .ts files
+dist/
+test/*.js
+test/*.d.ts
+js/*.js
+js/*.d.ts
+js/wasm
+.vscode
+pkg/

packages/wasm-dot/.gitignore

@@ -0,0 +1,5 @@
+{
+  "extensions": ["ts", "tsx", "js", "jsx"],
+  "spec": ["test/**/*.ts"],
+  "node-option": ["import=tsx/esm", "experimental-wasm-modules"]
+}

packages/wasm-dot/.mocharc.json

@@ -0,0 +1,4 @@
+js/wasm
+test/fixtures/
+target/
+bips/