fix(vscode): avoid regenerating notices during install

[yiliang114]

What this PR does

Stops normal dependency installation from regenerating the tracked VS Code companion notices. Notice generation remains explicit at the two points that need it: CI validation and VSIX packaging.

Why it's needed

The companion workspace's prepare script ran during npm ci, so a normal dependency install could rewrite NOTICES.txt and leave an unrelated working-tree change. Removing that install-time hook keeps installs and ordinary builds clean without allowing stale notices to merge or ship.

Reviewer Test Plan

How to verify

From a clean checkout, install dependencies and run an ordinary build. Confirm that NOTICES.txt is unchanged. Then package the VS Code companion and confirm that prepackage explicitly generates notices, the generated file still matches the tracked copy, and the VSIX contains it. Dependency changes that require a notices update should continue to fail the existing CI drift check until the regenerated file is committed.

Evidence (Before & After)

N/A (non-UI lifecycle change).

Tested on

OS	Status
🍏 macOS	✅
🪟 Windows	N/A
🐧 Linux	N/A

Environment (optional)

macOS with Node.js 22.22.0. Verified a clean npm ci including the full root build, companion lint/typecheck/build, explicit notice regeneration with no drift, and a complete VSIX package through the real npm run package lifecycle.

Risk & Scope

• Main risk or tradeoff: dependency updates rely on the existing explicit CI and packaging generation points instead of install-time generation.
• Not validated / out of scope: local packaging on Windows and Linux; the release workflow uses the same prepackage entrypoint on every target.
• Breaking changes / migration notes: none.

Linked Issues

Follow-up to #7161.

[github-actions]

Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration.

中文

请勿对活跃的 PR 执行 rebase 或 force-push，因为这会使已有的评审评论失效。另外，供日后参考：作为集成流程的一部分，机器人始终会自动将所有改动压缩（squash）为单个提交。