refactor(subtitles): inject default rules into SubtitleRuleSet.resolve()

aggregates.py used to call SubtitleKnowledgeBase().default_rules() via a
DEFAULT_RULES() helper, which silently pulled the infrastructure layer
(YAML loader) into the domain on every resolve.

Make the dependency explicit: resolve() now takes the default rules as
a parameter, and the caller (the ManageSubtitles use case) loads them
from the KB once and passes them in. Domain stays I/O-free.

- Drop DEFAULT_RULES helper and the SubtitleKnowledgeBase import from
  alfred/domain/subtitles/aggregates.py
- SubtitleRuleSet.resolve(default_rules: SubtitleMatchingRules)
- manage_subtitles use case passes kb.default_rules() at the call site
- Tests use a local SubtitleMatchingRules stand-in instead of relying
  on KB defaults

tests/domain/test_subtitle_utils.py

@@ -30,9 +30,19 @@ from alfred.domain.subtitles.value_objects import (
     RuleScope,
     SubtitleFormat,
     SubtitleLanguage,
+    SubtitleMatchingRules,
     SubtitleType,
 )
 
+# Test fixture: stand-in for what the KB would provide at runtime.
+_DEFAULT_RULES = SubtitleMatchingRules(
+    preferred_languages=["eng"],
+    preferred_formats=["srt"],
+    allowed_types=["standard"],
+    format_priority=["srt", "ass"],
+    min_confidence=0.7,
+)
+
 # --------------------------------------------------------------------------- #
 # Value objects                                                                #
 # --------------------------------------------------------------------------- #
@@ -230,18 +240,17 @@ class TestAvailableSubtitles:
 
 
 class TestSubtitleRuleSet:
-    def test_global_default_uses_kb_defaults(self):
+    def test_global_default_returns_injected_defaults(self):
         rs = SubtitleRuleSet.global_default()
-        rules = rs.resolve()
-        # Loaded from subtitles.yaml — defaults must be non-empty.
-        assert rules.preferred_languages
-        assert rules.preferred_formats
-        assert 0 < rules.min_confidence <= 1
+        rules = rs.resolve(_DEFAULT_RULES)
+        assert rules.preferred_languages == _DEFAULT_RULES.preferred_languages
+        assert rules.preferred_formats == _DEFAULT_RULES.preferred_formats
+        assert rules.min_confidence == _DEFAULT_RULES.min_confidence
 
     def test_override_persists(self):
         rs = SubtitleRuleSet.global_default()
         rs.override(languages=["eng"], min_confidence=0.9)
-        rules = rs.resolve()
+        rules = rs.resolve(_DEFAULT_RULES)
         assert rules.preferred_languages == ["eng"]
         assert rules.min_confidence == 0.9
 
@@ -252,10 +261,10 @@ class TestSubtitleRuleSet:
             parent=parent,
         )
         child.override(languages=["jpn"])
-        rules = child.resolve()
+        rules = child.resolve(_DEFAULT_RULES)
         assert rules.preferred_languages == ["jpn"]
         # min_confidence not overridden at child or parent → falls back to defaults
-        assert rules.min_confidence == parent.resolve().min_confidence
+        assert rules.min_confidence == parent.resolve(_DEFAULT_RULES).min_confidence
 
     def test_to_dict_only_emits_set_deltas(self):
         rs = SubtitleRuleSet(scope=RuleScope(level="show", identifier="tt1"))
@@ -286,4 +295,4 @@ class TestSubtitleRuleSet:
         # code uses `is not None` explicitly. Verify 0.0 doesn't fall back.
         rs = SubtitleRuleSet.global_default()
         rs.override(min_confidence=0.0)
-        assert rs.resolve().min_confidence == 0.0
+        assert rs.resolve(_DEFAULT_RULES).min_confidence == 0.0