feat: add archiving flows for sessions and workspaces

Users previously had an all-or-nothing choice for completed sessions: either keep them in the active
sidebar or permanently delete them. That made long-lived usage brittle because valuable history
stayed in the way unless users destroyed it. This change introduces archiving as a first-class
lifecycle so completed work can be hidden without losing transcript history, workspace context,
or restoreability.

The backend now persists session archive state and excludes archived rows from active session
queries by default. Dedicated archive queries and routes make archived sessions and archived
workspaces addressable on their own, which is necessary once hidden data can no longer be rebuilt
from the active project list. Hard-delete behavior still cleans up transcript files so destructive
deletes remain truly destructive.

The frontend now mirrors that lifecycle in the sidebar. Delete flows distinguish between archive
and permanent delete, archived sessions can be restored, archived workspaces appear beside
standalone archived sessions, and archived project sessions open with the correct workspace context
instead of routing to a session URL that leaves the main view empty. Follow-up archive UI polish
keeps the status affordances explicit without competing with workspace names.

server/modules/database/repositories/sessions.db.ts

@@ -8,13 +8,14 @@ type SessionRow = {
   project_path: string | null;
   jsonl_path: string | null;
   custom_name: string | null;
+  isArchived: number;
   created_at: string;
   updated_at: string;
 };
 
 type SessionMetadataLookupRow = Pick<
   SessionRow,
-  'session_id' | 'provider' | 'project_path' | 'jsonl_path' | 'custom_name' | 'created_at' | 'updated_at'
+  'session_id' | 'provider' | 'project_path' | 'jsonl_path' | 'custom_name' | 'isArchived' | 'created_at' | 'updated_at'
 >;
 
 function normalizeTimestamp(value?: string): string | null {
@@ -53,13 +54,14 @@ export const sessionsDb = {
     projectsDb.createProjectPath(normalizedProjectPath);
 
     db.prepare(
-      `INSERT INTO sessions (session_id, provider, custom_name, project_path, jsonl_path, created_at, updated_at)
-       VALUES (?, ?, ?, ?, ?, COALESCE(?, CURRENT_TIMESTAMP), COALESCE(?, CURRENT_TIMESTAMP))
+      `INSERT INTO sessions (session_id, provider, custom_name, project_path, jsonl_path, isArchived, created_at, updated_at)
+       VALUES (?, ?, ?, ?, ?, 0, COALESCE(?, CURRENT_TIMESTAMP), COALESCE(?, CURRENT_TIMESTAMP))
        ON CONFLICT(session_id) DO UPDATE SET
          provider = excluded.provider,
          updated_at = excluded.updated_at,
          project_path = excluded.project_path,
          jsonl_path = excluded.jsonl_path,
+         isArchived = 0,
          custom_name = COALESCE(excluded.custom_name, sessions.custom_name)`
     ).run(
       sessionId,
@@ -87,7 +89,7 @@ export const sessionsDb = {
     const db = getConnection();
     const row = db
       .prepare(
-        `SELECT session_id, provider, project_path, jsonl_path, custom_name, created_at, updated_at
+        `SELECT session_id, provider, project_path, jsonl_path, custom_name, isArchived, created_at, updated_at
          FROM sessions
          WHERE session_id = ?
          ORDER BY updated_at DESC
@@ -102,8 +104,25 @@ export const sessionsDb = {
     const db = getConnection();
     return db
       .prepare(
-        `SELECT session_id, provider, project_path, jsonl_path, custom_name, created_at, updated_at
-         FROM sessions`
+        `SELECT session_id, provider, project_path, jsonl_path, custom_name, isArchived, created_at, updated_at
+         FROM sessions
+         WHERE isArchived = 0`
+      )
+      .all() as SessionRow[];
+  },
+
+  /**
+   * Archived rows are intentionally queried separately so the caller can render
+   * them in a dedicated view without reintroducing them into active session lists.
+   */
+  getArchivedSessions(): SessionRow[] {
+    const db = getConnection();
+    return db
+      .prepare(
+        `SELECT session_id, provider, project_path, jsonl_path, custom_name, isArchived, created_at, updated_at
+         FROM sessions
+         WHERE isArchived = 1
+         ORDER BY datetime(COALESCE(updated_at, created_at)) DESC, session_id DESC`
       )
       .all() as SessionRow[];
   },
@@ -113,7 +132,24 @@ export const sessionsDb = {
     const normalizedProjectPath = normalizeProjectPath(projectPath);
     return db
       .prepare(
-        `SELECT session_id, provider, project_path, jsonl_path, custom_name, created_at, updated_at
+        `SELECT session_id, provider, project_path, jsonl_path, custom_name, isArchived, created_at, updated_at
+         FROM sessions
+         WHERE project_path = ?
+           AND isArchived = 0`
+      )
+      .all(normalizedProjectPath) as SessionRow[];
+  },
+
+  /**
+   * Permanent project deletion must see every session row for the path,
+   * including archived ones, so their transcript files can be cleaned up.
+   */
+  getSessionsByProjectPathIncludingArchived(projectPath: string): SessionRow[] {
+    const db = getConnection();
+    const normalizedProjectPath = normalizeProjectPath(projectPath);
+    return db
+      .prepare(
+        `SELECT session_id, provider, project_path, jsonl_path, custom_name, isArchived, created_at, updated_at
          FROM sessions
          WHERE project_path = ?`
       )
@@ -125,9 +161,10 @@ export const sessionsDb = {
     const normalizedProjectPath = normalizeProjectPath(projectPath);
     return db
       .prepare(
-        `SELECT session_id, provider, project_path, jsonl_path, custom_name, created_at, updated_at
+        `SELECT session_id, provider, project_path, jsonl_path, custom_name, isArchived, created_at, updated_at
          FROM sessions
          WHERE project_path = ?
+           AND isArchived = 0
          ORDER BY datetime(COALESCE(updated_at, created_at)) DESC, session_id DESC
          LIMIT ? OFFSET ?`
       )
@@ -141,7 +178,8 @@ export const sessionsDb = {
       .prepare(
         `SELECT COUNT(*) AS count
          FROM sessions
-         WHERE project_path = ?`
+         WHERE project_path = ?
+           AND isArchived = 0`
       )
       .get(normalizedProjectPath) as { count: number } | undefined;
 
@@ -167,6 +205,19 @@ export const sessionsDb = {
     return row?.custom_name ?? null;
   },
 
+  /**
+   * Soft-delete and restore both use the same flag update so callers keep the
+   * row, metadata, and file path intact while toggling visibility.
+   */
+  updateSessionIsArchived(sessionId: string, isArchived: boolean): void {
+    const db = getConnection();
+    db.prepare(
+      `UPDATE sessions
+       SET isArchived = ?
+       WHERE session_id = ?`
+    ).run(isArchived ? 1 : 0, sessionId);
+  },
+
   deleteSessionById(sessionId: string): boolean {
     const db = getConnection();
     return db.prepare('DELETE FROM sessions WHERE session_id = ?').run(sessionId).changes > 0;