feat(tools): implement CRUD operations for thoughts and projects

* Add tools for creating, retrieving, updating, and deleting thoughts.
* Implement project management tools for creating and listing projects.
* Introduce linking functionality between thoughts.
* Add search and recall capabilities for thoughts based on semantic queries.
* Implement statistics and summarization tools for thought analysis.
* Create database migrations for thoughts, projects, and links.
* Add helper functions for UUID parsing and project resolution.

internal/session/active_project.go

@@ -0,0 +1,37 @@
+package session
+
+import (
+	"sync"
+
+	"github.com/google/uuid"
+)
+
+type ActiveProjects struct {
+	mu        sync.RWMutex
+	bySession map[string]uuid.UUID
+}
+
+func NewActiveProjects() *ActiveProjects {
+	return &ActiveProjects{
+		bySession: map[string]uuid.UUID{},
+	}
+}
+
+func (a *ActiveProjects) Set(sessionID string, projectID uuid.UUID) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	a.bySession[sessionID] = projectID
+}
+
+func (a *ActiveProjects) Get(sessionID string) (uuid.UUID, bool) {
+	a.mu.RLock()
+	defer a.mu.RUnlock()
+	projectID, ok := a.bySession[sessionID]
+	return projectID, ok
+}
+
+func (a *ActiveProjects) Clear(sessionID string) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	delete(a.bySession, sessionID)
+}

internal/session/active_project_test.go

@@ -0,0 +1,27 @@
+package session
+
+import (
+	"testing"
+
+	"github.com/google/uuid"
+)
+
+func TestActiveProjectsSetGetClear(t *testing.T) {
+	store := NewActiveProjects()
+	projectID := uuid.New()
+
+	if _, ok := store.Get("session-1"); ok {
+		t.Fatal("Get() before Set() = true, want false")
+	}
+
+	store.Set("session-1", projectID)
+	got, ok := store.Get("session-1")
+	if !ok || got != projectID {
+		t.Fatalf("Get() = (%v, %v), want (%v, true)", got, ok, projectID)
+	}
+
+	store.Clear("session-1")
+	if _, ok := store.Get("session-1"); ok {
+		t.Fatal("Get() after Clear() = true, want false")
+	}
+}