Add ClientOSError retry handling to nanapi client

[Copilot]

Bot crashes with ClientOSError: [Errno 104] Connection reset by peer during nanapi calls. The client uses predicate-based backoff for HTTP status codes but lacks exception-based backoff for connection-level failures.

Changes

• nanachan/utils/misc.py: Add ClientOSError to conn_backoff exception tuple; export conn_backoff and timeout_backoff for reuse

• nanachan/nanapi/client.py: Compose timeout_backoff(conn_backoff) and apply to request chain in both load_bearer_token() and get_nanapi()

Retry Strategy

Request chain now handles (outermost to innermost):

1. Connection errors (ClientOSError, ClientConnectorError, etc.) → exponential backoff, max 600s
2. Timeout errors → exponential backoff, max 300s, 5 attempts
3. Auth errors (401) → token refresh, max 2 attempts
4. Status errors (502, 520, 522) → exponential backoff

# Before: only status-based retries
session._request = auth_backoff(session_backoff(wrap_request(session._request)))

# After: connection errors also retried
session._request = conn_exception_backoff(
    auth_backoff(session_backoff(wrap_request(session._request)))
)

Original prompt

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This section details on the original issue you should resolve

<issue_title>[autoreport] aiohttp.client_exceptions.ClientOSError: [Errno 104] Connection reset by peer</issue_title>
<issue_description>## Traceback

Traceback (most recent call last):
  File "/usr/local/lib/python3.14/asyncio/selector_events.py", line 1009, in _read_ready__data_received
    data = self._sock.recv(self.max_size)
ConnectionResetError: [Errno 104] Connection reset by peer

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/app/.venv/lib/python3.14/site-packages/discord/client.py", line 504, in _run_event
    await coro(*args, **kwargs)
  File "/app/nanachan/extensions/waicolle.py", line 2515, in on_user_message
    resp = await get_nanapi().waicolle.waicolle_add_player_coins(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        str(ctx.author.id), AddPlayerCoinsBody(moecoins=moecoin_gain)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/app/nanachan/nanapi/_client.py", line 4548, in waicolle_add_player_coins
    async with self.session.post(
               ~~~~~~~~~~~~~~~~~^
        url,
        ^^^^
        params=params,
        ^^^^^^^^^^^^^^
        json=body,
        ^^^^^^^^^^
    ) as resp:
    ^
  File "/app/.venv/lib/python3.14/site-packages/aiohttp/client.py", line 1510, in __aenter__
    self._resp: _RetType = await self._coro
                           ^^^^^^^^^^^^^^^^
  File "/app/.venv/lib/python3.14/site-packages/backoff/_async.py", line 76, in retry
    ret = await target(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/.venv/lib/python3.14/site-packages/backoff/_async.py", line 76, in retry
    ret = await target(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/nanachan/nanapi/client.py", line 73, in _wrapped
    return await _request(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/.venv/lib/python3.14/site-packages/aiohttp/client.py", line 779, in _request
    resp = await handler(req)
           ^^^^^^^^^^^^^^^^^^
  File "/app/.venv/lib/python3.14/site-packages/aiohttp/client.py", line 757, in _connect_and_send_request
    await resp.start(conn)
  File "/app/.venv/lib/python3.14/site-packages/aiohttp/client_reqrep.py", line 539, in start
    message, payload = await protocol.read()  # type: ignore[union-attr]
                       ^^^^^^^^^^^^^^^^^^^^^
  File "/app/.venv/lib/python3.14/site-packages/aiohttp/streams.py", line 680, in read
    await self._waiter
aiohttp.client_exceptions.ClientOSError: [Errno 104] Connection reset by peer

Initial user interaction

None

Comments on the Issue (you are @copilot in this section)

• Fixes [autoreport] aiohttp.client_exceptions.ClientOSError: [Errno 104] Connection reset by peer #115

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