HTTP API: layout

One misplaced artifact: a path found in a half whose declared layout excludes it, with the contract that excludes it and why, so a refusal names what to move and where it belongs.

It travels as the JSON of the layout.check capability, so its member names are the wire contract every projection reads:

use majordomus_cli::layout::LayoutFinding;
let finding = LayoutFinding {
    path: ".ai/local/notes/rule.md".into(),
    contract: "manifest local".into(),
    excludes: "canonical".into(),
    reason: "a copy of .ai/repo/rules/rule.md".into(),
};
let json = serde_json::to_value(&finding).unwrap();
assert_eq!(json["contract"], "manifest local");
assert_eq!(json["excludes"], "canonical");
let back: LayoutFinding = serde_json::from_value(json).unwrap();
assert_eq!(back, finding);

The answer of the layout check: whether the halves were read, how many paths were judged, and every path a contract excludes. A report that could not read the halves never passes, so silence about a tree nobody measured cannot read as a clean tree.

use majordomus_cli::layout::LayoutReport;
let clean = LayoutReport::of(true, None, 12, Vec::new());
assert!(clean.passes);
assert_eq!(clean.checked, 12);
let unread = LayoutReport::of(false, Some("git could not start".into()), 0, Vec::new());
assert!(!unread.passes, "nothing found because nothing was read");
assert_eq!(unread.reason.as_deref(), Some("git could not start"));