Function fail_unit 

pub fn fail_unit(
    mana_dir: &Path,
    id: &str,
    reason: Option<String>,
) -> Result<Unit, Error>

Mark a unit as explicitly failed without closing it.

Releases the claim, finalizes the current attempt as Failed, appends a structured failure summary to notes, and returns the unit to Open status for retry.

Errors

• anyhow::Error — unit not found or I/O failure

Example

use mana_core::api::fail_unit;
use std::path::Path;

let unit = fail_unit(Path::new("/project/.mana"), "1",
    Some("Blocked by missing auth token".to_string())).unwrap();
assert_eq!(unit.status, mana_core::api::Status::Open);