chore: bump typescript to 6.0

[justlevine]

What

Bumps typescript to latest. Updates the configs accordingly.

Why

General maint

Related Issue(s):

How

Testing Instructions

Screenshots

Additional Info

Checklist

• [x I have read the Contribution Guidelines.
• My PR title is descriptive and follows the conventional commit message format.
• My code passes all lints (PHPCS, PHPStan, ESLint, etc.).
• My code has detailed inline documentation.
• My code has tests that cover the changes I made.
• I have updated the project documentation as needed.

[Copilot]

Pull request overview

This PR upgrades the repository’s TypeScript toolchain to v6 and adjusts TypeScript configuration files to align with the new compiler defaults and project needs.

Changes:

• Bump typescript to ^6.0.3 and refresh package-lock.json dependency resolutions.
• Simplify/adjust TS compiler configuration in tsconfig.base.json and related project tsconfigs.
• Add global ambient module declarations for importing *.scss / *.css from TypeScript.

Reviewed changes

Copilot reviewed 3 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tsconfig.json	Updates project TS config; adjusts path mapping and compiler options.
tsconfig.base.json	Removes redundant/now-default strictness + interop compiler flags.
tests/js/tsconfig.json	Simplifies test TS config compilerOptions.
src/global.d.ts	Adds ambient declarations for stylesheet imports.
package.json	Bumps typescript devDependency to ^6.0.3.
package-lock.json	Updates lockfile to reflect the TS bump and transitive dependency updates.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.20%. Comparing base (665fb9c) to head (f713fb4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #36      +/-   ##
============================================
- Coverage     94.94%   94.20%   -0.74%     
  Complexity      115      115              
============================================
  Files            21       21              
  Lines           475      518      +43     
============================================
+ Hits            451      488      +37     
- Misses           24       30       +6     

Flag	Coverage Δ
unit	94.20% <ø> (-0.74%)	⬇️

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