docs: update README, CHANGELOG, CLAUDE.md, AGENTS.md for Tier 3-4 features (xAI, Voyage AI, gateway lock, shell completion, tailscale serve, DM pairing, lane queue, credential redaction, usage dashboard)

CHANGELOG.md

@@ -6,6 +6,35 @@ All notable changes to Flynn are documented in this file.
 
 ### Added
 
+- **xAI (Grok) Provider** -- xAI as OpenAI-compatible model provider with
+  `provider: xai` config. Supports grok-3, grok-3-mini, grok-2, grok-2-mini,
+  grok-3-fast. Uses `XAI_API_KEY` env var or config `api_key`.
+- **Voyage AI Embeddings** -- Voyage AI embedding provider for memory vector
+  search. OpenAI-compatible API at `https://api.voyageai.com/v1`, defaults to
+  1024 dimensions. Uses `VOYAGE_API_KEY` env var.
+- **Lane Queue** -- Per-session FIFO queue in the gateway that serializes
+  concurrent requests instead of rejecting them. Ensures ordered execution
+  within each session. 9 tests.
+- **Credential Redaction** -- Expanded `redactConfig()` from 2 to 18+ secret
+  fields: all channel tokens, model tier api_keys, embedding keys, webhook
+  secrets, Gmail credentials, MCP server env vars.
+- **Web UI Token Dashboard** -- New Usage page in the web dashboard SPA with
+  summary cards (total tokens, cost, sessions), per-session breakdown table,
+  and 10s auto-refresh. New `system.tokenUsage` gateway endpoint.
+- **Gateway Lock** -- Single-client mode for the WebSocket gateway. When
+  `server.lock: true`, only one connection allowed at a time; additional
+  connections rejected with close code 4003. Web UI detects locked state. 4 tests.
+- **Shell Completion** -- `flynn completion <shell>` command generating bash,
+  zsh, and fish completions. `--install` flag writes to the appropriate shell
+  config file. 11 tests.
+- **Tailscale Serve** -- Auto-expose gateway via `tailscale serve` on daemon
+  start. `isTailscaleAvailable()` check, auto-start/stop lifecycle, `flynn
+  doctor` integration. 6 tests.
+- **DM Pairing Codes** -- PairingManager with time-limited codes for
+  authenticating unknown DM senders. Integrated into all 4 channel adapters
+  (Telegram, Discord, Slack, WhatsApp). Gateway handlers (`pairing.generate`,
+  `pairing.list`, `pairing.revoke`). TUI `/pair` command. Configurable TTL
+  and code length. 22 tests.
 - **Zhipu AI (GLM) Provider** -- Support for Zhipu AI's GLM models (glm-4.5, glm-4.7, etc.)
   via their OpenAI-compatible API at `https://api.z.ai/api/paas/v4`. Uses `provider: zhipuai`
   in config with `api_key` or `ZHIPUAI_API_KEY` env var.