host: review fixes for cargo.build, the test runner, the console, and main; tests for every PROTOCOL.md rule

cargo.build and the runner (review T22R): builds use the network again;
core.unlock and core.notify in order under the runner; quiet test
output; manifest preparation keeps [workspace], target tables, renamed
and optional entries; cargo.rpc.discover; -32004 with data.output;
retention of 10 builds; light, empty test worlds with an in-memory
journal; only CARGO_/RUST_/SAUSAGE_ variables; stdin is null; the runner
through --config. A compile cache that cannot be created is not fatal.
Activation replaces plugin.wasm without a gap.

Console and main: init ships the workspace Cargo.lock and creates the
world atomically; each console command runs in its own task, so ps,
stop, and kill work during a slow call; SAUSAGE_HEADLESS; the terminal
mode is restored; signals during boot; chat text is not taken as a
command.

Tests: 20 more tests for PROTOCOL.md sections 2 to 10; the cargo tests
choose the libtest binary from cargo's JSON output and time out.

PROTOCOL.md

@@ -190,6 +190,7 @@ The standard JSON-RPC codes apply. The core adds these codes:
 | -32001 | There is no such plugin. |
 | -32002 | The process ended without an answer. `data` has the exit status and the last journal lines. |
 | -32003 | The activation was rejected. `data` has the reasons. |
+| -32004 | `cargo.build` failed. `data` has the `output` of the failed step and the `tests`. |
 
 ## 4. The filesystem