Function apply_fragment_to_file 

pub fn apply_fragment_to_file(
    path: &Path,
    fragment: &str,
    placement: FragmentPlacement,
    unique: bool,
    mode: ApplyMode,
    guard: Option<&PathGuard>,
) -> Result<EditResult>

Apply a freeform fragment at a required placement anchor on disk (#2032).

Strips Morph-style lazy marker lines (// ... existing code ...), then inserts after/before the unique anchor or replaces old via the same plan desugar path as CLI/MCP (plan_apply_fragment_to_replace → tx). Fail-closed: missing/ambiguous anchors, empty fragment after strip, PathGuard rejects.

Example

use patchloom::api::{
    ApplyMode, FragmentPlacement, apply_fragment_to_file,
};
use std::path::Path;

let _ = apply_fragment_to_file(
    Path::new("src/lib.rs"),
    "// ... existing code ...\nfn new() {}\n// ... existing code ...\n",
    FragmentPlacement::After("fn foo() {".into()),
    true,
    ApplyMode::Apply,
    None,
)?;