feat(sdk): TypeScript client — @engram/client npm package

[JamesJi79]

TypeScript SDK — @engram/client

This PR implements a complete TypeScript SDK mirroring the Python engram.sdk package, as requested in #22.

What's Included

Feature	Status	Python Equivalent
EngramClient (ingest, query, get, delete, list, health)	✅	EngramClient
Private namespaces (X25519 ECDH + HKDF + AES-256-GCM)	✅	HybridEncryption
Password-based encryption (legacy)	✅	NamespaceEncryption
sr25519 request signing via @polkadot/util-crypto	✅	sign_request()
CID parsing and validation	✅	parse_cid()
Error hierarchy	✅	EngramError, MinerOfflineError, etc.
Batch ingest (JSONL)	✅	batch_ingest_file()
Conversation ingest	✅	ingest_conversation()
URL fetch + ingest	✅	ingest_url()
Query by text or vector	✅	query(), query_by_vector()
Health check + isOnline	✅	health(), is_online()
Auto-discovery from subnet	🔜	from_subnet()

Package Structure

packages/engram-client/
├── package.json
├── tsconfig.json
├── README.md
├── src/
│   ├── index.ts        # entry point
│   ├── client.ts       # EngramClient (core)
│   ├── types.ts        # TypeScript type definitions
│   ├── errors.ts       # Error hierarchy
│   ├── encryption.ts   # X25519 + AES-256-GCM encryption
│   ├── namespace.ts    # sr25519 auth + signing
│   ├── cid.ts          # CID parsing/validation
│   └── utils.ts        # HTTP client helpers
└── tests/
    └── client.test.ts  # 18 unit tests

Tests

All 18 tests pass:

✓ CID parsing (4)
✓ Error classes (4)
✓ Encryption (3)
✓ Namespace auth (2)
✓ EngramClient (5)

Dependencies

• Runtime: @polkadot/util-crypto (sr25519 signing)
• Dev: typescript, vitest
• Zero runtime deps for core client — uses Node.js 18+ stdlib (fetch, crypto)

Integration Notes

• Uses crypto.diffieHellman() for X25519 ECDH (Node.js 18+)
• Fetch API for HTTP (Node.js 18+)
• To use sr25519 signing: npm install @polkadot/util-crypto (optional dep)
• Can be published to npm as @engram/client

Closes #22

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