core: review fixes, init builds the agent, console without a terminal

Activation path (review T6R): a broken plugin or a stray file in
/plugins blocks no activation; candidates replace their own entries;
discovery has a 10 s deadline and its process is stopped after the
answer; an unchanged hash keeps plugin.prev.wasm; activations run in
their own task; the watcher is not recursive; no duplicate services;
rpc.retired waits for live processes of its version; reads and hashes
on blocking threads.

Guest I/O and per-call paths: a stdin write error is EOF, stdout and
stderr are drained before the status; stderr is lossy UTF-8 and goes
to the journal from its own reader; compiled components are freed;
shutdown starts no new processes; lock queues drop stopping processes;
compile before the admission gate; CommandPre per component;
core.unlock in order; null errors are successes; the journal thread
survives SQLite errors.

sausage init builds the agent with cargo.build; sausage without a
command creates ./world. The console reads plain lines without a
terminal. PROTOCOL.md and DECISIONS.md describe the decided rules. The
flake tests the whole workspace and checks the packaged cargo.build.

cli/src/filesystem.rs

@@ -137,6 +137,8 @@ impl Proc {
 #[async_trait]
 impl Layer for Proc {
     async fn stat(&self, path: &str, follow: bool) -> Result<Stat> {
+        let path = path.trim_end_matches('/');
+        let path = if path.is_empty() { "/" } else { path };
         if matches!(path.trim_end_matches('/'), "" | "/core" | "/core/plugins") {
             return Ok(directory());
         }
@@ -147,6 +149,8 @@ impl Layer for Proc {
         folder.stat(&path, follow).await
     }
     async fn list(&self, path: &str) -> Result<Vec<Entry>> {
+        let path = path.trim_end_matches('/');
+        let path = if path.is_empty() { "/" } else { path };
         if path == "/" {
             let mut entries = vec![entry("core".into(), true)];
             entries.extend(self.0.processes().into_keys().map(|pid| entry(pid, true)));
@@ -176,6 +180,8 @@ impl Layer for Proc {
         folder.list(&path).await
     }
     async fn open(&self, path: &str, options: Open) -> Result<Arc<dyn File>> {
+        let path = path.trim_end_matches('/');
+        let path = if path.is_empty() { "/" } else { path };
         if options.write || options.create || options.truncate {
             return denied();
         }