feat(resolver): support inline #ref pin and default-branch alias

Adds the missing pieces for installer fixtures that pin a dev package
via `dev-foo#hex` or rely on Composer's `default-branch: true` synthetic
`9999999-dev` alias.

Mirrors Composer at four layers:

1. `mozart_semver::parse_single` strips `dev-...#hex` / `....x-dev#hex`
   suffixes from constraints (Composer's `parseConstraint` regex).
2. `PackagistVersion` carries `default_branch`. When set on a `dev-`
   package with no numeric prefix, `packagist_to_pool_inputs` emits
   the synthetic `9999999-dev` alias — but skips it when an explicit
   `extra.branch-alias` already covers the version (matches
   `ArrayLoader::getBranchAlias`).
3. `RuleSetGenerator::generate` picks up `addRulesForRootAliases`:
   any pool alias whose target was added gets its own alias↔target
   rules so the SAT solver pulls them in together.
4. `lockfile::generate_lock_file` extracts root `#hex` overrides from
   `require`/`require-dev` and rewrites source/dist references (and
   github/gitlab/bitbucket archive URLs) on the matched package, the
   `setSourceDistReferences` ladder Composer runs in `PoolBuilder`.

Resolver also infers `Stability::Dev` from a `dev-foo` style
single-atom constraint when no explicit `@flag` is given, mirroring
the second loop of `RootPackageLoader::extractStabilityFlags` so the
package isn't filtered out under default `stable` minimum-stability.

Newly green: install_branch_alias_composer_repo, install_reference,
conflict_with_alias_prevents_update_if_not_required,
unbounded_conflict_matches_default_branch.

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

1 files changed, 18 insertions, 0 deletions

diff --git a/crates/mozart-sat-resolver/src/rule_set_generator.rs b/crates/mozart-sat-resolver/src/rule_set_generator.rs
index b5dfcdb..92b9f77 100644
--- a/crates/mozart-sat-resolver/src/rule_set_generator.rs
+++ b/crates/mozart-sat-resolver/src/rule_set_generator.rs
@@ -105,6 +105,24 @@ impl<'a> RuleSetGenerator<'a> {
             }
         }
 
+        // Mirror Composer's `RuleSetGenerator::addRulesForRootAliases`:
+        // ensure every alias whose target was already added gets its own
+        // alias↔target rules, even when the alias itself didn't appear in
+        // any root require's `whatProvides` (e.g. the synthetic
+        // `9999999-dev` alias from a `default-branch: true` package, which
+        // only matches a literal `9999999-dev` constraint).
+        let alias_pairs: Vec<(PackageId, PackageId)> = self
+            .pool
+            .packages()
+            .iter()
+            .filter_map(|p| p.is_alias_of.map(|t| (p.id, t)))
+            .collect();
+        for (alias_id, target_id) in alias_pairs {
+            if self.added_map.contains(&target_id) && !self.added_map.contains(&alias_id) {
+                self.add_rules_for_package(alias_id);
+            }
+        }
+
         // Add conflict rules
         self.add_conflict_rules();