feat(gateway): WhatsApp inbound plain-text batching (Telegram-style)

[keiravoss94]

What does this PR do?

Adds adapter-level text batching for the WhatsApp gateway adapter so multiple plain-text bubbles (or rapid follow-ups) merge into one agent turn after a quiet period, matching the debounce behavior already used on Telegram, Discord, and Matrix.

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• gateway/platforms/whatsapp.py — debounced text batching with HERMES_WHATSAPP_TEXT_BATCH_DELAY_SECONDS (default 0.6)
• tests/gateway/test_text_batching.py — batching behavior tests
• tests/gateway/test_whatsapp_connect.py — disconnect cleanup for batch timers
• website/docs/reference/environment-variables.md — document batch delay env var
• website/docs/user-guide/messaging/whatsapp.md — document batching behavior

How to Test

1. uv run pytest -o addopts= tests/gateway/test_text_batching.py tests/gateway/test_whatsapp_connect.py -q
2. Send several rapid plain-text WhatsApp messages to the gateway — confirm they arrive as a single merged turn after the quiet period
3. Send a message with media or a long chunk — confirm it flushes immediately without waiting for unrelated batch slots

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

For New Skills

N/A — delete this section otherwise.

Screenshots / Logs

N/A

[teknium1]

Superseded by PR #35391 (merged, commit cddb728), which adds text-debounce batching to both WhatsApp and Weixin. The implementation was salvaged from @redpiggy-cyber's PR #35302 (both adapters) and adapted to the config.yaml path. Thanks for the earlier WhatsApp-only proposal here — closing as covered by the merged change.

#35391