Add messaging platform enhancements: STT, stickers, Discord UX, Slack, pairing, hooks

Major feature additions inspired by OpenClaw/ClawdBot integration analysis:

Voice Message Transcription (STT):
- Auto-transcribe voice/audio messages via OpenAI Whisper API
- Download voice to ~/.hermes/audio_cache/ on Telegram/Discord/WhatsApp
- Inject transcript as text so all models can understand voice input
- Configurable model (whisper-1, gpt-4o-mini-transcribe, gpt-4o-transcribe)

Telegram Sticker Understanding:
- Describe static stickers via vision tool with JSON-backed cache
- Cache keyed by file_unique_id avoids redundant API calls
- Animated/video stickers get emoji-based fallback description

Discord Rich UX:
- Native slash commands (/ask, /reset, /status, /stop) via app_commands
- Button-based exec approvals (Allow Once / Always Allow / Deny)
- ExecApprovalView with user authorization and timeout handling

Slack Integration:
- Full SlackAdapter using slack-bolt with Socket Mode
- DMs, channel messages (mention-gated), /hermes slash command
- File attachment handling with bot-token-authenticated downloads

DM Pairing System:
- Code-based user authorization as alternative to static allowlists
- 8-char codes from unambiguous alphabet, 1-hour expiry
- Rate limiting, lockout after failed attempts, chmod 0600 on data
- CLI: hermes pairing list/approve/revoke/clear-pending

Event Hook System:
- File-based hook discovery from ~/.hermes/hooks/
- HOOK.yaml + handler.py per hook, sync/async handler support
- Events: gateway:startup, session:start/reset, agent:start/step/end
- Wildcard matching (command:* catches all command events)

Cross-Channel Messaging:
- send_message agent tool for delivering to any connected platform
- Enables cron job delivery and cross-platform notifications

Human-Like Response Pacing:
- Configurable delays between message chunks (off/natural/custom)
- HERMES_HUMAN_DELAY_MODE env var with min/max ms settings

Warm Injection Message Style:
- Retrofitted image vision messages with friendly kawaii-consistent tone
- All new injection messages (STT, stickers, errors) use warm style

Also: updated config migration to prompt for optional keys interactively,
bumped config version, updated README, AGENTS.md, .env.example,
cli-config.yaml.example, install scripts, pyproject.toml, and toolsets.

.env.example

@@ -140,6 +140,36 @@ BROWSER_INACTIVITY_TIMEOUT=120
 # Format: logs/session_YYYYMMDD_HHMMSS_UUID.json
 # Contains full conversation history in trajectory format for debugging/replay
 
+# =============================================================================
+# VOICE TRANSCRIPTION (Speech-to-Text)
+# =============================================================================
+# Required for automatic voice message transcription on messaging platforms.
+# Uses OpenAI's Whisper API directly (not via OpenRouter).
+# Get at: https://platform.openai.com/api-keys
+OPENAI_API_KEY=
+
+# =============================================================================
+# SLACK INTEGRATION
+# =============================================================================
+# Slack Bot Token - From Slack App settings (OAuth & Permissions)
+# Get at: https://api.slack.com/apps
+# SLACK_BOT_TOKEN=xoxb-...
+
+# Slack App Token - For Socket Mode (App-Level Tokens in Slack App settings)
+# SLACK_APP_TOKEN=xapp-...
+
+# Slack allowed users (comma-separated Slack user IDs)
+# SLACK_ALLOWED_USERS=
+
+# =============================================================================
+# RESPONSE PACING
+# =============================================================================
+# Human-like delays between message chunks on messaging platforms.
+# Makes the bot feel less robotic.
+# HERMES_HUMAN_DELAY_MODE=off     # off | natural | custom
+# HERMES_HUMAN_DELAY_MIN_MS=800   # Min delay in ms (custom mode)
+# HERMES_HUMAN_DELAY_MAX_MS=2500  # Max delay in ms (custom mode)
+
 # =============================================================================
 # LEGACY/OPTIONAL API KEYS
 # =============================================================================