feat(bot): add modality map, config loader, and backend client

Implements core bot infrastructure:
- modality_map: channel name to modality string mapping (personal_text, voice, fb_messenger, nd_messenger)
- config: Config dataclass with env-driven configuration loading for Discord, backend, and email IMAP credentials
- backend_client: async HTTP client for posting items to backend /items endpoint

All modality_map tests passing (3/3)

bot/chorus_bot/backend_client.py

@@ -0,0 +1,28 @@
+from datetime import datetime
+import httpx
+
+
+class BackendClient:
+    def __init__(self, base_url: str):
+        self._base_url = base_url.rstrip("/")
+
+    async def create_item(
+        self,
+        *,
+        modality: str,
+        raw_content: str,
+        captured_at: datetime,
+        discord_message_id: str | None,
+        sender_id: str | None = None,
+    ) -> dict:
+        payload = {
+            "modality": modality,
+            "raw_content": raw_content,
+            "captured_at": captured_at.isoformat(),
+            "discord_message_id": discord_message_id,
+            "sender_id": sender_id,
+        }
+        async with httpx.AsyncClient() as client:
+            resp = await client.post(f"{self._base_url}/items", json=payload, timeout=10)
+            resp.raise_for_status()
+            return resp.json()

bot/chorus_bot/config.py

@@ -0,0 +1,45 @@
+import os
+from dataclasses import dataclass
+
+
+@dataclass
+class Config:
+    discord_token: str
+    guild_id: int
+    inbox_channel_id: int
+    triage_role_id: int
+    backend_base_url: str
+    google_voice_imap_host: str
+    google_voice_imap_user: str
+    google_voice_imap_password: str
+    bh_email_imap_host: str
+    bh_email_imap_user: str
+    bh_email_imap_password: str
+    personal_email_imap_host: str
+    personal_email_imap_user: str
+    personal_email_imap_password: str
+
+
+def load_config() -> Config:
+    def env(name: str) -> str:
+        value = os.environ.get(name)
+        if not value:
+            raise RuntimeError(f"Missing required env var: {name}")
+        return value
+
+    return Config(
+        discord_token=env("CHORUS_DISCORD_TOKEN"),
+        guild_id=int(env("CHORUS_GUILD_ID")),
+        inbox_channel_id=int(env("CHORUS_INBOX_CHANNEL_ID")),
+        triage_role_id=int(env("CHORUS_TRIAGE_ROLE_ID")),
+        backend_base_url=env("CHORUS_BACKEND_BASE_URL"),
+        google_voice_imap_host=env("CHORUS_GVOICE_IMAP_HOST"),
+        google_voice_imap_user=env("CHORUS_GVOICE_IMAP_USER"),
+        google_voice_imap_password=env("CHORUS_GVOICE_IMAP_PASSWORD"),
+        bh_email_imap_host=env("CHORUS_BH_EMAIL_IMAP_HOST"),
+        bh_email_imap_user=env("CHORUS_BH_EMAIL_IMAP_USER"),
+        bh_email_imap_password=env("CHORUS_BH_EMAIL_IMAP_PASSWORD"),
+        personal_email_imap_host=env("CHORUS_PERSONAL_EMAIL_IMAP_HOST"),
+        personal_email_imap_user=env("CHORUS_PERSONAL_EMAIL_IMAP_USER"),
+        personal_email_imap_password=env("CHORUS_PERSONAL_EMAIL_IMAP_PASSWORD"),
+    )

bot/chorus_bot/modality_map.py

@@ -0,0 +1,10 @@
+CHANNEL_TO_MODALITY = {
+    "personal-text": "personal_text",
+    "voice": "voice",
+    "fb-messenger": "fb_messenger",
+    "nd-messenger": "nd_messenger",
+}
+
+
+def modality_for_channel(channel_name: str) -> str | None:
+    return CHANNEL_TO_MODALITY.get(channel_name)

bot/requirements.txt

@@ -0,0 +1,5 @@
+discord.py==2.4.0
+httpx==0.27.2
+aioimaplib==1.1.0
+pytest==8.3.3
+pytest-asyncio==0.24.0

bot/tests/test_modality_map.py

@@ -0,0 +1,17 @@
+from chorus_bot import modality_map
+
+
+def test_known_channels_map_to_modalities():
+    assert modality_map.modality_for_channel("personal-text") == "personal_text"
+    assert modality_map.modality_for_channel("voice") == "voice"
+    assert modality_map.modality_for_channel("fb-messenger") == "fb_messenger"
+    assert modality_map.modality_for_channel("nd-messenger") == "nd_messenger"
+
+
+def test_unknown_channel_returns_none():
+    assert modality_map.modality_for_channel("random-chat") is None
+
+
+def test_inbox_and_general_channels_are_not_mapped():
+    assert modality_map.modality_for_channel("inbox") is None
+    assert modality_map.modality_for_channel("general") is None