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.

examples/notes-v2/Cargo.lock

@@ -18,6 +18,7 @@ checksum = "cf8baf1c55e62ffcace7a9f06f4bd9cd3f0c4beb022d3b367256b91b87513d98"
 name = "notes"
 version = "0.1.0"
 dependencies = [
+ "sausage-actor",
  "serde_json",
 ]
 
@@ -39,6 +40,14 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "sausage-actor"
+version = "0.1.0"
+dependencies = [
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "serde"
 version = "1.0.229"
@@ -46,6 +55,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4148590afebada386688f18773da617792bf2ef03ffc1e4cbd2b1d45b023e0ba"
 dependencies = [
  "serde_core",
+ "serde_derive",
 ]
 
 [[package]]