feat: merge upstream chat features with enhanced rate limiting and relay

[hunmar]

This PR enhances the upstream feature/ephemeral-chat branch with additional features for better rate limiting, local testing support, and comprehensive documentation.

Key Additions

• Advanced Rate Limiting: Cooldown (2s) + burst limit (5 messages/30s) with visual UI feedback
• Nickname System: Optional ephemeral nicknames stored in localStorage
• TCP Relay Server: Workaround for DHT discovery issues in WSL2/Docker environments
• Visual Cooldown Timer: Input blocking with countdown display during rate limit
• AGENTS.md: Comprehensive documentation for AI coding agents (800+ lines)

Changes from Upstream

New Files

File	Description
AGENTS.md	Deep technical documentation for AI agents
relay-server.js	Simple TCP relay for local multi-node testing
src/state/ratelimit.js	ChatRateLimiter class with burst + cooldown logic

Enhanced Features

Feature	Upstream	This PR
Rate Limiting	Simple 5s cooldown	2s cooldown + 5/30s burst limit
Rate Limit UI	Prompt color change	Disabled input + countdown timer
Nicknames	None	Optional, localStorage persisted
Local Testing	DHT only	DHT + TCP relay fallback
Documentation	README only	README + AGENTS.md

Technical Changes

• src/config/constants.js: Added CHAT_MIN_COOLDOWN, CHAT_BURST_LIMIT, CHAT_BURST_WINDOW, CHAT_MAX_LENGTH, CHAT_NICK_MAX_LENGTH
• src/p2p/swarm.js: Added RELAY_PORT support, connectToRelay(), getAllConnections()
• src/p2p/messaging.js: Integrated ChatRateLimiter, signature verification for chat
• src/web/routes.js: Enhanced /api/chat with rate limiting and nickname support
• public/app.js: Cooldown timer UI, nickname modal, improved message display
• public/index.html: Nickname modal, cooldown indicator element
• public/style.css: Cooldown animation, nickname modal styling

Protocol Enhancement

CHAT Message Format

{
  "type": "CHAT",
  "id": "<node-public-key>",
  "nick": "optional_nickname",
  "msg": "message content",
  "ts": 1704326400000,
  "hops": 0,
  "nonce": 12345,
  "sig": "<signature of 'chat:${msg}:${ts}'>"
}

Rate Limiting Rules

• Cooldown: 2 seconds between messages
• Burst: Maximum 5 messages per 30-second window
• Response: 429 with cooldown field in milliseconds

Local Testing with TCP Relay

For environments where DHT discovery fails (WSL2, Docker, corporate networks):

# Terminal 1 - Start relay
node relay-server.js

# Terminal 2 - Node 1
RELAY_PORT=4000 ENABLE_CHAT=true PORT=3000 node server.js

# Terminal 3 - Node 2
RELAY_PORT=4000 ENABLE_CHAT=true PORT=3001 node server.js

Cooldown Timer

When rate limited, the input is disabled and shows remaining seconds:

• Orange pulsing countdown (e.g., "1.8s")
• Input field grayed out
• Re-enables automatically when cooldown ends

Nickname Modal

Click [set nick] to open modal:

• Alphanumeric only, max 16 characters
• Persists in localStorage across sessions

Test Plan

• npm install && npm start — node starts without errors
• Open dashboard with ENABLE_CHAT=true — chat panel visible
• Send message — appears in chat, cooldown timer starts
• Rapid messages — input disabled, timer counts down
• Set nickname — persists after refresh
• Two-node relay test:

  node relay-server.js &
  RELAY_PORT=4000 ENABLE_CHAT=true PORT=3000 node server.js &
  RELAY_PORT=4000 ENABLE_CHAT=true PORT=3001 node server.js

• Messages propagate between nodes via relay
• direct count shows 1 (relay connection counted)

Breaking Changes

None. All changes are additive and backward compatible with existing nodes.

Related PR

#20

[DataDalton]

Please remove agents.md, I recommend opening a new PR and creating proper documentation for humans, otherwise you're grouping too much into a single PR