fix(samples): supply --subagent_urls and sub-agent ports in demo:orchestrator

[retz8]

Description

This fixes #586.

Changes to samples/client/lit/package.json:

• serve:agent:orchestrator: adds the required --subagent_urls flags (localhost:10003/10004/10005)
• demo:orchestrator: now starts all five services — shell client, the three sub-agents on explicit ports, and
  the orchestrator

Service	Port	Color
Shell client	5173	magenta
restaurant_finder	10003 (overrides default 10002)	blue
contact_lookup	10004	green
rizzcharts	10005 (overrides default 10002)	yellow
orchestrator	10002	cyan

Demo

After Running following commands,

cd samples/client/lit
export GEMINI_API_KEY="..."
npm install
npm run demo:orchestrator

terminal shows...

1. Shell Running on 5173

2. Sub-agents running on different ports

3. Orchestrator fetches agents cards from sub agents

4. Orchestrator is now ready and running on 10002

Pre-launch Checklist

• I signed the [CLA].
• I read the [Contributors Guide].
• I read the [Style Guide].
• I have added updates to the [CHANGELOG].
• I updated/added relevant documentation.
• My code changes (if any) have tests.

[gemini-code-assist]

Code Review

This pull request fixes the demo:orchestrator script by correctly configuring and launching the orchestrator and its sub-agents. The changes in package.json add the necessary --subagent_urls and set explicit ports for the sub-agents. My review includes a suggestion to refactor the demo:orchestrator script to improve maintainability by reusing existing npm scripts, which will reduce code duplication.

[zeroasterisk]

@nan-yu after your PR #759 please review this one