refactor: switch internal maps/sets from HashMap to IndexMap

Adopt indexmap workspace-wide so iteration order is deterministic and
follows insertion order. The non-deterministic order of std HashMap
otherwise leaks into resolver decisions when multiple valid solutions
exist (e.g. cyclic require pairs under prefer-lowest), making behavior
flaky and divergent from Composer's PHP-array semantics.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/crates/mozart/src/commands/search.rs b/crates/mozart/src/commands/search.rs
index accd6af..023bfdf 100644
--- a/crates/mozart/src/commands/search.rs
+++ b/crates/mozart/src/commands/search.rs
@@ -139,7 +139,7 @@ pub async fn execute(
 
         // Deduplicate to unique vendor names (Composer returns vendor-only names
         // for SEARCH_VENDOR mode).
-        let mut seen = std::collections::HashSet::new();
+        let mut seen = indexmap::IndexSet::new();
         let mut vendor_names: Vec<String> = Vec::new();
         for r in &results {
             let vendor = r.name.split('/').next().unwrap_or("").to_string();
@@ -515,7 +515,7 @@ mod tests {
         ];
         let refs: Vec<&SearchResult> = results.iter().collect();
 
-        let mut seen = std::collections::HashSet::new();
+        let mut seen = indexmap::IndexSet::new();
         let mut vendor_names: Vec<String> = Vec::new();
         for r in &refs {
             let vendor = r.name.split('/').next().unwrap_or("").to_string();