chore: add VS Code workspace foundation

[josiahking]

Summary

Adds the EvolvePHP 2 Phase 2.8 developer-experience and VS Code workspace foundation.

Changes

• adds repository-root .editorconfig
• adds minimal VS Code extension recommendations
• adds portable VS Code workspace settings
• adds convenience tasks backed by existing Composer workspace commands
• targets PHP 8.4 language analysis in Intelephense
• documents VS Code and integrated-terminal requirements
• distinguishes non-mutating quality checks from explicit Style Fix
• adds developer-experience policy coverage
• records Phase 2.8 in the changelog

VS Code Tasks

• EvolvePHP 2: Install Workspace Dependencies
• EvolvePHP 2: Quality
• EvolvePHP 2: Tests
• EvolvePHP 2: Architecture
• EvolvePHP 2: Static Analysis
• EvolvePHP 2: Style Check
• EvolvePHP 2: Style Fix
• EvolvePHP 2: Root Policy

The tasks reuse the existing repository-owned Composer commands rather than duplicating PHPStan, Deptrac, PHP-CS-Fixer or PHPUnit configuration.

Portability

• no local PHP executable path
• no local Composer executable path
• no user-specific filesystem paths
• no automatic PHP formatting on save
• no runtime/Xdebug launch configuration
• no .code-workspace
• no new dependencies

Contributors must make PHP 8.4+ and Composer available through their VS Code integrated terminal environment.

Validation

• developer-experience policy: 10 tests, 182 assertions
• README consistency: 13 tests, 130 assertions
• RFC consistency: 11 tests, 126 assertions
• Documentation: 105 tests, 1,118 assertions
• Architecture: 47 tests, 2,881 assertions
• complete root suite: 152 tests, 3,999 assertions
• PHP 8.4 CI policy: 152 tests, 3,999 assertions
• workspace PHPUnit: 6 tests, 18 assertions
• Deptrac: 0 violations
• PHPStan: no errors
• PHP-CS-Fixer: 0 files fixable
• aggregate workspace quality passed
• VS Code JSON validation passed
• git diff --check passed

Scope

Exactly eight files:

• .editorconfig
• .vscode/extensions.json
• .vscode/settings.json
• .vscode/tasks.json
• CHANGELOG.md
• README.md
• tests/Documentation/EvolvePhp2DeveloperExperienceTest.php
• workspace/README.md

No Composer manifest, lockfile, workflow, package, RFC, runtime or GitHub-setting changes are included.