Fall back to software volume when PulseAudio is unreachable (#143)

## Summary
- Add `async_check_available()` to `hardware_volume.py` that tests
actual PulseAudio connectivity, not just library import
- In `cli.py`, use the runtime check before starting — if PulseAudio
isn't reachable, disable hardware volume upfront with a warning
- In `audio_connector.py`, add a safety net in `read_initial_volume()`
so if PulseAudio fails at runtime, it falls back to software volume
instead of crashing

Fixes #141

## Test plan
- [ ] On Linux with PulseAudio running: hardware volume should work as
before
- [ ] On Linux without PulseAudio running: should log a warning and fall
back to software volume
- [ ] On Linux without `pulsectl-asyncio` installed + `--hardware-volume
true`: should still raise a clear error asking the user to install the
library
- [ ] Daemon mode auto-detection: should only enable hardware volume if
PulseAudio is actually reachable

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: balloob

sendspin/cli.py

@@ -13,6 +13,7 @@
 from typing import TYPE_CHECKING
 
 from sendspin.hardware_volume import AVAILABLE as HW_VOLUME_AVAILABLE
+from sendspin.hardware_volume import async_check_available as hw_volume_check_available
 from sendspin.settings import ClientSettings, get_client_settings, get_serve_settings
 
 if TYPE_CHECKING:
@@ -600,6 +601,10 @@ async def _run_client_mode(args: argparse.Namespace) -> int:
     # Set up logging with resolved log level
     logging.basicConfig(level=getattr(logging, args.log_level))
 
+    if args.hardware_volume and not await hw_volume_check_available():
+        LOGGER.warning("PulseAudio server not reachable, falling back to software volume control")
+        args.hardware_volume = False
+
     # Handle daemon subcommand
     if args.command == "daemon":
         return await _run_daemon_mode(args, settings)

sendspin/hardware_volume.py

@@ -23,6 +23,27 @@
 VolumeChangeCallback = Callable[[int, bool], None]
 
 
+async def async_check_available(timeout: float = 2.0) -> bool:
+    """Check if PulseAudio is actually reachable at runtime.
+
+    Returns True only if we can connect to the PulseAudio server.
+    This goes beyond the module-level AVAILABLE check (which only verifies
+    the library is installed) by testing the actual connection. The check
+    is bounded by *timeout* seconds to keep CLI startup responsive when
+    PulseAudio is down or unreachable.
+    """
+    if not AVAILABLE:
+        return False
+
+    try:
+        async with asyncio.timeout(timeout):
+            async with pulsectl_asyncio.PulseAsync("sendspin-cli-check") as client:
+                await client.server_info()
+        return True
+    except Exception:  # noqa: BLE001
+        return False
+
+
 class HardwareVolumeController:
     """Controls Linux system output volume through PulseAudio API.