Deduplicate layout script tags and enforce JS dependency order

[VatsalSy]

Why

Multiple PRs repeatedly surfaced duplicate script includes and dependency-order regressions across layouts.

Evidence

• PR JavaScript optimization: eliminate redundancy and improve performance #58 reviews: duplicate includes (main.js, command-palette.js) and missing utils.js/search-manager.js in some layouts.
• PR Harden content and script maintenance safeguards #62 review: duplicate command-palette.js include noted in teaching layout.

Scope

• Audit _layouts/*.html for duplicated script tags.
• Ensure dependency order: utils.js and search-manager.js load before scripts that consume them.
• Remove redundant includes in affected layouts (teaching, teaching-course, team, research, history as needed).
• Add a small CI guard script/check to catch duplicate includes and order violations.

Acceptance Criteria

• No layout has duplicate includes for main.js or command-palette.js.
• Pages depending on window.Utils and window.SearchManager always load those first.
• CI fails when duplicate includes or invalid ordering is introduced.