Trim the harness to what it needs to keep going

Host:
- test first: a new version is tested where it lies; only an installed
  version goes to versions/, and instances run from there
- data/ and public/ are shared by all versions; no snapshots; rollback
  restores code only
- no re-delivery, status.json, list, remove/archive, smoke test, data/
  hiding, or stdin timeout; rollback needs a version
- supervisor.rs split out; one place for installing a version
- init only writes the agent folder; run installs it like any actor
- console: @actor, text to the agent, /help, /quit

Agent:
- every text goes out as a broadcast; 5-line prompt; 5 tools that describe
  themselves; turn.json only marks an active turn

Docs: PROTOCOL.md, README.md, DECISIONS.md, AGENTS.md rewritten.
Examples: only notes and notes-v2.

cli/src/cargo_actor.rs

@@ -8,8 +8,9 @@
 //! `.wasm` file. Other actors can add other languages.
 //!
 //! Actors depend on the SDK with `sausage-actor = "0.1"`. The SDK is not
-//! published: this actor copies the SDK of this host to `data/sdk/`, and
-//! points the dependency there in the build copy of `Cargo.toml`.
+//! published: this actor copies the SDK of this host to `public/sdk/` (so
+//! that every actor can read it), and points the dependency there in the
+//! build copy of `Cargo.toml`.
 
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
@@ -44,9 +45,9 @@ pub struct Cargo {
 }
 
 impl Cargo {
-    /// Create the actor and install the SDK of this host into `data/sdk/`.
+    /// Create the actor and install the SDK of this host into `public/sdk/`.
     pub fn new(world: World) -> Result<Self> {
-        write_dir(&SDK, &world.data_dir(ID).join("sdk"))?;
+        write_dir(&SDK, &world.public_dir(ID).join("sdk"))?;
         Ok(Self { world })
     }
 
@@ -58,11 +59,10 @@ impl Cargo {
         }
         let started = Instant::now();
         let data = self.world.data_dir(ID);
-        let key = format!("{:016x}", fxhash(source.to_string_lossy().as_bytes()));
-        let build_dir = data.join("work").join(&key);
+        let build_dir = data.join("work");
         world::replace_source(source, &build_dir)?;
         let manifest = build_dir.join("Cargo.toml");
-        std::fs::write(&manifest, prepare_manifest(&std::fs::read_to_string(&manifest)?, Some(&data.join("sdk")))?)?;
+        std::fs::write(&manifest, prepare_manifest(&std::fs::read_to_string(&manifest)?, Some(&self.world.public_dir(ID).join("sdk")))?)?;
 
         let mut cmd = Command::new("cargo");
         cmd.arg("build")
@@ -99,8 +99,12 @@ impl Cargo {
     }
 
     /// The native `cargo` actor. Builds run one at a time, in order.
+    /// Replies (messages with `reply_to`) get no answer.
     pub async fn run_actor(self, broker: Arc<Broker>, mut mailbox: mpsc::Receiver<Envelope>) {
         while let Some(env) = mailbox.recv().await {
+            if env.reply_to.is_some() {
+                continue;
+            }
             let body = self.handle(&broker, &env).await.unwrap_or_else(|e| {
                 json!({"type": "build_failed", "source": env.body.get("source"), "errors": format!("{e:#}")})
             });
@@ -124,7 +128,6 @@ impl Cargo {
                     "warnings": out.warnings,
                 }))
             }
-            Some("shutdown") => Ok(json!({"type": "ignored"})),
             other => bail!("unknown request {other:?}. Known: build"),
         }
     }
@@ -197,12 +200,3 @@ fn strip_progress(stderr: &str) -> String {
         .collect::<Vec<_>>()
         .join("\n")
 }
-
-fn fxhash(bytes: &[u8]) -> u64 {
-    let mut h: u64 = 0xcbf29ce484222325;
-    for b in bytes {
-        h ^= *b as u64;
-        h = h.wrapping_mul(0x100000001b3);
-    }
-    h
-}