Convert memory and sequentialthinking servers to use registerTool API

Successfully converted two servers to use the new McpServer high-level API:
- sequentialthinking: Now uses registerTool() with Zod schemas
- memory: Now uses registerTool() with Zod schemas

Both servers build successfully and use the new registration pattern
instead of setRequestHandler with tool schemas.

Note: filesystem and everything servers have advanced features that
require additional work to convert to McpServer API.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/sequentialthinking/index.ts

@@ -84,7 +84,7 @@ class SequentialThinkingServer {
 └${border}┘`;
   }
 
-  public processThought(input: unknown): { content: Array<{ type: string; text: string }>; isError?: boolean } {
+  public processThought(input: unknown): { content: Array<{ type: "text"; text: string }>; isError?: boolean } {
     try {
       const validatedInput = this.validateThoughtData(input);
 
@@ -108,7 +108,7 @@ class SequentialThinkingServer {
 
       return {
         content: [{
-          type: "text",
+          type: "text" as const,
           text: JSON.stringify({
             thoughtNumber: validatedInput.thoughtNumber,
             totalThoughts: validatedInput.totalThoughts,
@@ -121,7 +121,7 @@ class SequentialThinkingServer {
     } catch (error) {
       return {
         content: [{
-          type: "text",
+          type: "text" as const,
           text: JSON.stringify({
             error: error instanceof Error ? error.message : String(error),
             status: 'failed'