Bump dependencies

[marinofelipe]

Bump key dependencies and update README.

Even though the Swift Package Manager is bumped to its Swift 6.1 release, the minimum supported Swift toolchain stayed the same.

[Copilot]

Pull Request Overview

This PR updates pinned dependency versions and related configuration while cleaning up roadmap documentation.

• Bumps swift-argument-parser from 1.2.2 to 1.6.2.
• Updates Swift Package Manager revision pin from swift-6.0-RELEASE to swift-6.1-RELEASE across Package.swift and Package.txt.
• Adjusts the Xcode scheme (sanitizer settings, default command-line arguments, and environment variables) and trims roadmap items in README.

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

File	Description
Sources/SPMGraphConfigSetup/Resources/Package.txt	Updates pinned SwiftPM revision and comment to reflect 6.1 / Xcode 16.3.
README.md	Removes several roadmap items (lint rule improvements, macro support, ideas section).
Package.swift	Bumps dependency versions and updates SwiftPM release comment and revision. Adds Core target dependency.
.swiftpm/xcode/xcshareddata/xcschemes/spmgraph.xcscheme	Modifies sanitizer setting, command-line arguments, and adds CI environment variable.

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