feat(phase-2.2): synthesis activities (5 activities)

Activities for the synthesis workflow pipeline:
  1. ChunkAndEmbedActivity — deterministic chunk ID + ingest via memory service
  2. ExtractEntitiesActivity — wiki-link, proper noun, technical term extraction
  3. ExtractFactsActivity — verb pattern matching (uses/runs/has/is/depends_on)
  4. DetectContradictionsActivity — query existing facts + pre-filter contradictions
  5. PersistSynthesisActivity — save entities + facts to memory service

Entity extraction patterns:
  - [[WikiLinks]] → 0.95 confidence
  - ProperNouns → 0.70 confidence
  - TECHNICAL_TERMS/camelCase → 0.65 confidence
  - Deduplication across patterns

Fact extraction:
  - 6 verb patterns (uses, runs_on, has, is, depends_on, connects_to)
  - Confidence boost when subject/object are known entities

Contradiction detection:
  - Query memory service for existing facts about same subject
  - Pre-filter: subject match + different object
  - Severity: low/medium/high based on similarity score
  - Auto-resolve low severity, queue review for medium/high

Tests: 10 pass (wiki links, proper nouns, tech terms, dedup,
       verb patterns, empty text, contradicts, contains, common, classify)
Build: clean, 35 packages pass

activity/synthesis_test.go

@@ -0,0 +1,130 @@
+package activity
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var testCtx = context.Background()
+
+func TestExtractEntities_WikiLinks(t *testing.T) {
+	sa := NewSynthesisActivities(nil) // No client needed for extraction
+	entities, err := sa.ExtractEntitiesActivity(testCtx, "chunk-1", "Deploy [[Kubernetes]] with [[ArgoCD]]")
+	assert.NoError(t, err)
+
+	names := entityNames(entities)
+	assert.Contains(t, names, "Kubernetes")
+	assert.Contains(t, names, "ArgoCD")
+
+	// Wiki links get high confidence
+	for _, e := range entities {
+		if e.Name == "Kubernetes" || e.Name == "ArgoCD" {
+			assert.Equal(t, 0.95, e.Confidence)
+			assert.Equal(t, "reference", e.EntityType)
+		}
+	}
+}
+
+func TestExtractEntities_ProperNouns(t *testing.T) {
+	sa := NewSynthesisActivities(nil)
+	entities, err := sa.ExtractEntitiesActivity(testCtx, "chunk-2", "Redis runs on Ubuntu Server")
+	assert.NoError(t, err)
+
+	names := entityNames(entities)
+	assert.Contains(t, names, "Redis")
+	assert.Contains(t, names, "Ubuntu Server")
+}
+
+func TestExtractEntities_TechnicalTerms(t *testing.T) {
+	sa := NewSynthesisActivities(nil)
+	entities, err := sa.ExtractEntitiesActivity(testCtx, "chunk-3", "Set MAX_RETRIES and use camelCase variables")
+	assert.NoError(t, err)
+
+	names := entityNames(entities)
+	assert.Contains(t, names, "MAX_RETRIES")
+	assert.Contains(t, names, "camelCase")
+}
+
+func TestExtractEntities_Deduplication(t *testing.T) {
+	sa := NewSynthesisActivities(nil)
+	entities, err := sa.ExtractEntitiesActivity(testCtx, "chunk-4", "[[Redis]] uses Redis for caching")
+	assert.NoError(t, err)
+
+	count := 0
+	for _, e := range entities {
+		if e.Name == "Redis" {
+			count++
+		}
+	}
+	assert.Equal(t, 1, count, "Redis should appear only once")
+}
+
+func TestExtractFacts_VerbPatterns(t *testing.T) {
+	sa := NewSynthesisActivities(nil)
+	entities := []ExtractedEntity{
+		{Name: "Kubernetes", EntityType: "tool"},
+		{Name: "Docker", EntityType: "tool"},
+	}
+	facts, err := sa.ExtractFactsActivity(testCtx, "chunk-5",
+		"Kubernetes uses Docker for container runtime. Redis depends on TCP",
+		entities)
+	assert.NoError(t, err)
+	assert.Greater(t, len(facts), 0)
+
+	// Find the "uses" fact
+	found := false
+	for _, f := range facts {
+		if f.Predicate == "uses" && f.Subject == "Kubernetes" {
+			found = true
+			assert.Greater(t, f.Confidence, 0.7) // Boosted by known entities
+		}
+	}
+	assert.True(t, found, "should find Kubernetes uses Docker fact")
+}
+
+func TestExtractFacts_EmptyText(t *testing.T) {
+	sa := NewSynthesisActivities(nil)
+	facts, err := sa.ExtractFactsActivity(testCtx, "chunk-6", "", nil)
+	assert.NoError(t, err)
+	assert.Empty(t, facts)
+}
+
+func TestContradicts(t *testing.T) {
+	assert.True(t, contradicts("Kubernetes uses port 8080", ExtractedFact{
+		Subject: "Kubernetes", Predicate: "uses_port", Object: "9090",
+	}))
+
+	assert.False(t, contradicts("Kubernetes uses port 8080", ExtractedFact{
+		Subject: "Kubernetes", Predicate: "uses_port", Object: "8080",
+	}))
+}
+
+func TestContainsSubject(t *testing.T) {
+	assert.True(t, containsSubject("Kubernetes runs on Linux", "kubernetes"))
+	assert.False(t, containsSubject("Docker runs on Linux", "kubernetes"))
+}
+
+func TestIsCommonWord(t *testing.T) {
+	assert.True(t, isCommonWord("The"))
+	assert.True(t, isCommonWord("This"))
+	assert.False(t, isCommonWord("Kubernetes"))
+	assert.False(t, isCommonWord("Redis"))
+}
+
+func TestClassifyEntity(t *testing.T) {
+	assert.Equal(t, "tool", classifyEntity("Kubernetes"))
+	assert.Equal(t, "tool", classifyEntity("Docker"))
+	assert.Equal(t, "tool", classifyEntity("Redis"))
+	assert.Equal(t, "concept", classifyEntity("SomeRandomThing"))
+}
+
+// helper
+func entityNames(entities []ExtractedEntity) []string {
+	names := make([]string, len(entities))
+	for i, e := range entities {
+		names[i] = e.Name
+	}
+	return names
+}