chore: replace Claude with Letta

.letta/settings.json

···
+{
+  "localSharedBlockIds": {
+    "project": "block-19ad1e80-37cd-4413-8f73-e1dddbb89119",
+    "skills": "block-25b184a7-e851-42d4-bf5a-9422337e7803"
+  }
+}

.letta/settings.local.json

···
+{
+  "lastAgent": "agent-2470875d-24da-4bab-8670-293b3cbcf3cf"
+}

CLAUDE.md

···
-# CLAUDE.md
-
-This file provides guidance to Claude Code (claude.ai/code) when working with
-code in this repository.
-
-## Commands
-
-### Testing
-
-```bash
-# Run all tests across the monorepo
-deno test --allow-env
-
-# Run tests for a specific package
-deno test packages/crypto/
-
-# Run E2E tests (requires CISTERN_HANDLE and CISTERN_APP_PASSWORD environment variables)
-deno test --allow-env --allow-net e2e.test.ts
-```
-
-### Lexicon Code Generation
-
-```bash
-# Generate TypeScript types from JSON lexicon definitions
-cd packages/lexicon
-deno task generate
-```
-
-This generates types in `packages/lexicon/src/types/` from the JSON schemas in
-`packages/lexicon/lexicons/`. Run this after modifying any `.json` files in the
-lexicons directory.
-
-### Type Checking
-
-```bash
-# Deno executes TypeScript directly - no build step needed
-# Check types explicitly with:
-deno check <file.ts>
-```
-
-## Architecture Overview
-
-Cistern is a **Deno monorepo** implementing a private, encrypted quick-capture
-system on AT Protocol. Items are end-to-end encrypted using post-quantum
-cryptography and stored temporarily in the user's PDS (Personal Data Server).
-
-### Monorepo Structure
-
-Five packages with clear separation of concerns:
-
-- **`@cistern/crypto`** - Core cryptographic primitives
-  (encryption/decryption/keys)
-- **`@cistern/lexicon`** - AT Protocol schema definitions (pubkey + item
-  records)
-- **`@cistern/shared`** - Authentication utilities and common code
-- **`@cistern/producer`** - Creates and encrypts items for storage
-- **`@cistern/consumer`** - Retrieves, decrypts, and deletes items
-
-Internal imports use the `@cistern/*` namespace defined in each package's
-`deno.jsonc`.
-
-### Producer/Consumer Pattern
-
-**Producer** workflow (packages/producer/mod.ts):
-
-1. Select a public key from those registered in the user's PDS
-2. Encrypt plaintext using the public key
-3. Create an `app.cistern.lexicon.item` record with the encrypted payload
-4. Upload to PDS
-
-**Consumer** workflow (packages/consumer/mod.ts):
-
-1. Generate an X-Wing keypair (post-quantum)
-2. Upload public key to PDS as `app.cistern.lexicon.pubkey` record
-3. Keep private key locally (never uploaded)
-4. Retrieve items via **polling** (`listItems()`) or **streaming**
-   (`subscribeToItems()`)
-5. Decrypt items matching the local keypair
-6. Delete items after consumption
-
-### Encryption Architecture
-
-**Algorithm**: `x_wing-xchacha20_poly1305-sha3_512`
-
-The encryption system uses a hybrid approach combining:
-
-- **X-Wing KEM** (Key Encapsulation Mechanism) - post-quantum hybrid combining
-  ML-KEM-768 and X25519
-- **XChaCha20-Poly1305** - authenticated encryption cipher
-- **SHA3-512** - content integrity verification
-
-**Encryption flow** (packages/crypto/src/encrypt.ts):
-
-1. X-Wing encapsulation generates a shared secret from the public key
-2. XChaCha20-Poly1305 encrypts the plaintext using the shared secret
-3. SHA3-512 hash computed for integrity verification
-4. Returns `EncryptedPayload` containing ciphertext, nonce, hash, and metadata
-
-**Decryption flow** (packages/crypto/src/decrypt.ts):
-
-1. X-Wing decapsulation recovers the shared secret using the private key
-2. XChaCha20-Poly1305 decrypts the content
-3. Integrity verification: check content length and SHA3-512 hash match
-4. Returns plaintext or throws error if verification fails
-
-### AT Protocol Integration
-
-Cistern uses two record types in the user's PDS:
-
-**`app.cistern.lexicon.pubkey`**
-(packages/lexicon/lexicons/app/cistern/lexicon/pubkey.json):
-
-- Stores public keys with human-readable names
-- Referenced by items via AT-URI
-- Schema: `{name, algorithm, content, createdAt}`
-
-**`app.cistern.lexicon.item`**
-(packages/lexicon/lexicons/app/cistern/lexicon/item.json):
-
-- Stores encrypted items temporarily
-- Schema:
-  `{tid, ciphertext, nonce, algorithm, pubkey, payload, contentLength, contentHash}`
-- The `pubkey` field is an AT-URI reference to the public key record
-
-### Real-time Streaming
-
-The consumer can subscribe to new items via **Jetstream**
-(packages/consumer/mod.ts:150-190):
-
-- Connects to Bluesky's Jetstream WebSocket service
-- Filters for `app.cistern.lexicon.item` creates matching user DID
-- Decrypts items as they arrive in real-time
-- Used for instant delivery (e.g., Obsidian plugin waiting for new memos)
-
-### Key Management
-
-**Private keys never leave the consumer's device.** The security model depends
-on:
-
-- Private key stored off-protocol (e.g., in an Obsidian vault)
-- Public key stored in PDS as a record
-- Items encrypted with public key can only be decrypted by matching private key
-- Each keypair can have a human-readable name (e.g., "Work Laptop", "Phone")
-
-### Dependencies
-
-**Cryptography** (JSR packages):
-
-- `@noble/post-quantum` - X-Wing KEM implementation
-- `@noble/ciphers` - XChaCha20-Poly1305
-- `@noble/hashes` - SHA3-512
-
-**AT Protocol** (npm packages):
-
-- `@atcute/client` - RPC client for PDS communication
-- `@atcute/jetstream` - Real-time event streaming
-- `@atcute/lexicons` - Schema validation
-- `@atcute/tid` - Timestamp identifiers
-
-## Key Files and Locations
-
-### Cryptographic Operations
-
-- `packages/crypto/src/keys.ts` - Keypair generation (X-Wing)
-- `packages/crypto/src/encrypt.ts` - Encryption logic
-- `packages/crypto/src/decrypt.ts` - Decryption + integrity verification
-- `packages/crypto/src/*.test.ts` - Crypto unit tests
-
-### Producer Implementation
-
-- `packages/producer/mod.ts` - Main producer class and encryption workflow
-
-### Consumer Implementation
-
-- `packages/consumer/mod.ts` - Keypair management, item retrieval, Jetstream
-  subscription
-
-### Authentication
-
-- `packages/shared/produce-requirements.ts` - DID resolution and session
-  creation
-- Uses Slingshot service for handle → DID resolution
-- Creates authenticated RPC client with app password
-
-### Schema Definitions
-
-- `packages/lexicon/lexicons/app/cistern/lexicon/*.json` - AT Protocol record
-  schemas
-- `packages/lexicon/src/types/` - Generated TypeScript types (run
-  `deno task generate` to update)
-- `packages/lexicon/lex.config.ts` - Lexicon generator configuration
-
-## Important Patterns
-
-### Error Handling in Decryption
-
-Decryption can fail for multiple reasons (packages/crypto/src/decrypt.ts):
-
-- Wrong private key (decapsulation fails)
-- Corrupted ciphertext (authentication fails)
-- Length mismatch (integrity check fails)
-- Hash mismatch (integrity check fails)
-
-Always wrap decrypt calls in try-catch and handle gracefully.
-
-### Pagination in Consumer
-
-`listItems()` returns an async generator that handles pagination automatically.
-It yields decrypted items and internally manages cursors. Consumers should
-iterate with `for await` loops.
-
-### Resource URIs
-
-AT Protocol uses AT-URIs to reference records: `at://<did>/<collection>/<rkey>`
-
-The consumer caches the public key's AT-URI with the local keypair to filter
-which items it can decrypt.
-
-## Testing
-
-### Unit Tests
-
-Each package contains unit tests following these conventions:
-- Test files use `.test.ts` suffix
-- Use `@std/expect` for assertions
-- Mock external dependencies (RPC clients, credentials)
-- Test both success and error paths
-
-**Test locations:**
-- `packages/crypto/src/*.test.ts` - Cryptographic operations
-- `packages/consumer/mod.test.ts` - Consumer functionality
-- `packages/producer/mod.test.ts` - Producer functionality
-
-### End-to-End Tests
-
-`e2e.test.ts` contains integration tests that use real AT Protocol credentials:
-- Requires `CISTERN_HANDLE` and `CISTERN_APP_PASSWORD` environment variables
-- Tests full workflow: keypair generation, encryption, decryption, deletion
-- Uses Deno test steps to segment each phase
-- Automatically skipped if environment variables are not set
-- Cleans up all test data after execution