[coverage-improver] Cover empty cache index and reconciler raw_content branches

[github-actions]

What branches were uncovered

1. libaipm/src/cache.rs — read_index(), line 383

if content.is_empty() {
    return Ok(CacheIndex::default());
}

The True branch (file exists but is empty) was never exercised. All existing tests that call read_index() do so after a put() which always writes a non-empty JSON index.

2. libaipm/src/migrate/reconciler.rs — find_associated_artifact(), line 112

if content.contains(path_str.as_ref()) {
    return Some(artifact.name.clone());
}

The True branch (raw_content contains the file path, returning an association) was not covered by any direct call to find_associated_artifact. While the through-reconcile() path was covered, one LLVM inlining context had True: 0.

What scenario the new tests cover

Test 1 — cache::tests::get_with_empty_index_file_returns_none:
Creates a cache, manually writes an empty cache_index.json file (simulating a truncated/reset cache), then calls cache.get(). The read_index() function finds the file, reads empty content, and returns CacheIndex::default() via the previously-uncovered early-return.

Test 2 — migrate::reconciler::tests::find_associated_artifact_raw_content_contains_path:
Calls find_associated_artifact directly with an artifact that has no referenced_scripts but whose raw_content contains the queried path string. This ensures the True branch of content.contains() is hit in the direct-call inlining context.

Before / after branch coverage

Metric	Before	After
Total branches	1940	1940
Missed branches	189	188
Branch coverage	90.26%	90.31%

Tests added

// cache.rs
#[test]
fn get_with_empty_index_file_returns_none() {
    let (temp, cache) = test_cache(Policy::Auto);
    let cache_root = temp.path().join("cache");
    std::fs::create_dir_all(&cache_root).unwrap_or_else(|_| {});
    std::fs::write(cache.index_path(), "").unwrap_or_else(|_| {});

    let result = cache.get("some-spec");
    assert!(result.is_ok());
    assert!(result.unwrap_or(Some(PathBuf::new())).is_none());
}

// reconciler.rs
#[test]
fn find_associated_artifact_raw_content_contains_path() {
    let mut artifact = make_artifact("config-skill", ArtifactKind::Skill, "/src/skills/cfg");
    artifact.metadata.raw_content = Some("assets/logo.png is referenced here".to_string());

    let result = find_associated_artifact(Path::new("assets/logo.png"), &[artifact]);
    assert_eq!(result, Some("config-skill".to_string()));
}

Generated by Coverage Improver · ● 5.9M · ◷

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.35%. Comparing base (64fd752) to head (743bd5d).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #280      +/-   ##
==========================================
+ Coverage   95.34%   95.35%   +0.01%     
==========================================
  Files          91       91              
  Lines       26467    26482      +15     
  Branches      805      805              
==========================================
+ Hits        25234    25251      +17     
+ Misses       1100     1099       -1     
+ Partials      133      132       -1     

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