brokerd: recall and memory, decided under built-in grants

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

crates/brokerd/src/builtin.rs

@@ -0,0 +1,45 @@
+//! The built-in grants of `recall` and `memory` (M5a spec, section 8). Reading and writing memory
+//! is what an agent is, so no grant file can turn it off or put questions in front of it; the
+//! prompt is protected by `memoryd`, which lets only clean sessions edit identity.
+
+use proto::{Grant, GrantProblem, sha256};
+
+use crate::grants::LoadedGrant;
+
+/// Ids starting with this are the built-ins'; an owner's grant file may not use one.
+pub const RESERVED: &str = "builtin-";
+
+/// The built-in grants' text, hashed for the audit log like a grant file's bytes.
+pub const RECALL: &str = "tool = \"recall\"\nmode = \"auto\"\nmax_taint = \"secret\"\nresult_class = \"private\"\nuntrusted = false\n";
+pub const MEMORY: &str = "tool = \"memory\"\nmode = \"auto\"\nmax_taint = \"secret\"\nresult_class = \"private\"\nuntrusted = false\n";
+
+/// The sentence for an owner's grant naming a memory tool.
+pub const BUILT_IN: &str = "the policy of recall and memory is built in; remove this grant";
+
+/// The two built-in grants, `builtin-memory` and `builtin-recall`.
+pub fn grants() -> Result<Vec<LoadedGrant>, GrantProblem> {
+    // For each (id, text) of [("builtin-memory", MEMORY), ("builtin-recall", RECALL)]:
+    // `toml::from_str::<Grant>(text)` and `sha256(text.as_bytes())`, each error as a GrantProblem {
+    // file: id, line: None, problem: e.to_string() }; build LoadedGrant { id, grant, sha256 }.
+    // Collect into Result<Vec<LoadedGrant>, GrantProblem> (the first error wins).
+    let sources: &[(&str, &str)] = &[("builtin-memory", MEMORY), ("builtin-recall", RECALL)];
+    let mut out: Vec<LoadedGrant> = Vec::new();
+    for (id, text) in sources {
+        let grant = toml::from_str::<Grant>(text).map_err(|error| GrantProblem {
+            file: id.to_string(),
+            line: None,
+            problem: error.to_string(),
+        })?;
+        let sha256 = sha256(text.as_bytes()).map_err(|error| GrantProblem {
+            file: id.to_string(),
+            line: None,
+            problem: error.to_string(),
+        })?;
+        out.push(LoadedGrant {
+            id: id.to_string(),
+            grant,
+            sha256,
+        });
+    }
+    Ok(out)
+}