fix: prevent spurious agent startup in dev mode and remove tiktoken dep

When running `agentcore dev` with multiple agents, useDevServer would
start the first agent's server before the user selected one, because
getDevConfig defaults to agents[0] when agentName is undefined. Guard
config resolution on agentName being set so the server only starts
after explicit selection.

Also remove tiktoken from the LangChain template dependencies as the
package no longer resolves correctly.

Author: tejaskash

src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap

@@ -2095,7 +2095,6 @@ dependencies = [
     "mcp >= 1.19.0",
     "langchain-mcp-adapters >= 0.1.11",
     "langchain >= 1.0.3",
-    "tiktoken == 0.11.0",
     "bedrock-agentcore >= 1.0.3",
     "botocore[crt] >= 1.35.0",
 {{#if (eq modelProvider "Bedrock")}}

src/assets/python/langchain_langgraph/base/pyproject.toml

@@ -15,7 +15,6 @@ dependencies = [
     "mcp >= 1.19.0",
     "langchain-mcp-adapters >= 0.1.11",
     "langchain >= 1.0.3",
-    "tiktoken == 0.11.0",
     "bedrock-agentcore >= 1.0.3",
     "botocore[crt] >= 1.35.0",
 {{#if (eq modelProvider "Bedrock")}}

src/cli/tui/hooks/useDevServer.ts

@@ -87,7 +87,7 @@ export function useDevServer(options: { workingDir: string; port: number; agentN
   }, [options.workingDir]);
 
   const config: DevConfig | null = useMemo(() => {
-    if (!project) {
+    if (!project || !options.agentName) {
       return null;
     }
     return getDevConfig(options.workingDir, project, configRoot, options.agentName);

src/schema/constants.ts

@@ -95,7 +95,6 @@ export const RESERVED_PROJECT_NAMES: readonly string[] = [
   'pytest',
   'pytestasyncio',
   'pythondotenv',
-  'tiktoken',
   // Build tools
   'hatchling',
   'setuptools',