channels: add tmux pane channel daemon

Standalone daemon that streams tmux pane output via pipe-pane
(no polling). Each configured pane becomes a channel "tmux.<label>"
accessible through the standard channel.capnp protocol.

- pipe-pane streams PTY output directly to FIFOs
- Async readers push new lines into ChannelLogs
- send works via tmux send-keys
- Cleanup disconnects pipe-pane on daemon exit

Config: ~/.consciousness/channels/tmux.json5
Socket: ~/.consciousness/channels/tmux.sock

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

channels/tmux/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "consciousness-channel-tmux"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+capnp = "0.20"
+capnp-rpc = "0.20"
+dirs = "6"
+libc = "0.2"
+scopeguard = "1"
+futures = "0.3"
+json5 = "0.4"
+poc-memory = { path = "../.." }
+serde = { version = "1", features = ["derive"] }
+tokio = { version = "1", features = ["full"] }
+tokio-util = { version = "0.7", features = ["compat"] }
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }