feat: add run() and binary entry points for all servers and init

Every server now has lib.rs (testable) + main.rs (deployable binary).
Binary is 3 lines: extern crate userspace_rt + call run().
Hardware servers use feature flags for adapter selection.
9 RISC-V binaries ready for the disk image.

crates/servers/session-server/Cargo.toml

@@ -3,7 +3,13 @@ name = "session-server"
 version = "0.1.0"
 edition = "2024"
 
+[[bin]]
+name = "session-server"
+test = false
+bench = false
+
 [dependencies]
 types = { workspace = true }
 userspace = { workspace = true }
+userspace-rt = { workspace = true }
 server-framework = { workspace = true }