chore(swift): drop per-user Xcode state, show demo screenshot in README

[lgalabru]

What

• Remove tracked per-user Xcode state. xcuserdata/ludo.xcuserdatad (personal scheme management) was committed under both swift/.swiftpm/… and the PayKitDemo xcodeproj. Removed both and added xcuserdata/ to swift/.gitignore so it can't be re-committed.
• Show the demo screenshot in the swift/README.md Examples section, under the PayKitDemo (SwiftUI iOS app) entry.

Shared schemes (xcshareddata/xcschemes/…) are intentionally kept — those are meant to be tracked.

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

This PR removes two accidentally-committed per-user Xcode state files (xcuserdata/ludo.xcuserdatad/) from both .swiftpm and the PayKitDemo Xcode project, adds xcuserdata/ to swift/.gitignore so the pattern can't recur, and embeds a demo screenshot in the swift/README.md Examples section.

• Gitignore hardening: xcuserdata/ is added to swift/.gitignore, which covers all nested .xcodeproj and .swiftpm paths; shared schemes under xcshareddata/ are intentionally untouched.
• Dead file removal: both deleted plists were developer-local only and one even contained a duplicate XML key, making their removal strictly correct.
• README update: the screenshot image is referenced via an absolute raw/main/ GitHub URL; the image file exists at the expected path in the repo.

Confidence Score: 5/5

Safe to merge — removes developer-local Xcode state, adds a gitignore guard, and embeds a screenshot in the README with no logic changes.

All changes are housekeeping: deleted files are personal Xcode metadata with no effect on build or runtime, the gitignore addition is correctly scoped, and the README image points to a file that already exists in the repo.

No files require special attention.

Important Files Changed

Filename	Overview
swift/.gitignore	Adds xcuserdata/ glob to prevent per-user Xcode state from being re-committed; correctly scoped to the swift/ subtree so it covers all nested .xcodeproj and .swiftpm directories.
swift/.swiftpm/xcode/xcuserdata/ludo.xcuserdatad/xcschemes/xcschememanagement.plist	Deletes a personal Xcode scheme-management plist that was inadvertently committed; no functional code removed.
swift/Examples/PayKitDemo/PayKitDemo.xcodeproj/xcuserdata/ludo.xcuserdatad/xcschemes/xcschememanagement.plist	Deletes a second personal Xcode scheme-management plist; the file also contained a duplicate XML key (PayKitDemo.xcscheme_^#shared#^_ appeared twice), so its removal is strictly an improvement.
swift/README.md	Inserts a centered screenshot of the PayKitDemo iOS app using a pinned raw/main/ GitHub URL; the referenced image file exists at the expected path.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Developer opens Xcode] --> B{Xcode writes xcuserdata/}
    B -->|Before this PR| C[xcuserdata/ tracked by git\nPersonal state committed]
    B -->|After this PR| D[xcuserdata/ in .gitignore\nPersonal state ignored]
    C --> E[Other contributors see\nludo's scheme ordering]
    D --> F[Each contributor keeps\ntheir own local state]
    G[xcshareddata/xcschemes/] -->|Still tracked| H[Shared schemes available\nto all contributors]

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_{Reviews (1): Last reviewed commit: "chore(swift): drop per-user Xcode state,..." | Re-trigger Greptile}

[EfeDurmaz16]

Drops the committed xcuserdata plists and gitignores them, keeps the shared schemes, adds the demo screenshot to the README. Nothing tracked that shouldn't be. LGTM.