feat: Shade E2EE library — M1-M3 complete

Signal Protocol implementation with full X3DH + Double Ratchet:

- M1: Core types, CryptoProvider interface, KDF chain functions,
  SubtleCrypto+noble/curves provider, MemoryStorage
- M2: X3DH key agreement (identity keys, signed prekeys, one-time
  prekeys, bundle processing for both initiator and responder)
- M3: Double Ratchet (symmetric-key ratchet, DH ratchet, skipped
  message key cache, out-of-order delivery, AAD-bound headers)

68 tests, 0 failures — including full integration test of
X3DH handshake → Double Ratchet conversation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -0,0 +1,20 @@
+{
+  "name": "shade",
+  "private": true,
+  "workspaces": ["packages/*"],
+  "scripts": {
+    "test": "bun test --recursive",
+    "test:core": "cd packages/shade-core && bun test",
+    "test:crypto": "cd packages/shade-crypto-web && bun test",
+    "test:proto": "cd packages/shade-proto && bun test",
+    "test:server": "cd packages/shade-server && bun test",
+    "test:transport": "cd packages/shade-transport && bun test"
+  },
+  "devDependencies": {
+    "bun-types": "^1.3.11"
+  },
+  "dependencies": {
+    "@noble/curves": "^2.0.1",
+    "@noble/hashes": "^2.0.1"
+  }
+}