[AadarshJena]

Closes #10

WHAT CHANGED

• Moved face tracking out of CameraView.swift into a new local package, apps/ios/Packages/GraptionVision, so it can be unit tested without a camera
• Face IDs are now strings f1, f2, ... (matches FaceId in the event schema) and are never reused within a session
• Matching follows section 6 of GRAPTION_CONTEXT.md: IoU of at least 0.3 first, then a center-distance fallback for fast movers (V2 used center distance only)
• A face that disappears keeps its ID for 2 seconds (V2 dropped it after 2 frames), so turning your head away and back keeps the same ID. A missed face is still only drawn for 2 frames so boxes don't linger
• Added a SpeakerScorer protocol and a LargestFaceScorer stub (biggest face = speaker). The Core ML speaker model will replace it behind the same protocol
• Camera overlay: each box shows its ID. The guessed speaker reads "fX talking" in green, others are yellow
• Rotating the phone or flipping the camera calls the new forgetTracks() (faces get new IDs, numbering keeps counting so an old ID can't land on someone else). Leaving the camera screen calls reset() (IDs restart at f1)
• One Euro smoothing and coasting logic moved unchanged from V2
• Linked the package in project.pbxproj. iOS CI now runs swift test on it
• Updated GRAPTION_CONTEXT.md section 6 (FaceTracker: 2 second memory and why, speaker guess)
• Works with P7 (match caption to speaker + tests #73) as is: captionSpeaker(from:during:) takes the f1 IDs and per-frame scores V3 produces

FUNCTIONALITY

• two faces get f1/f2, biggest face labelled "talking"
• labels stay with people walking past each other
• turning away until the box disappears, then back within 2 seconds, keeps the ID
• stepping closer moves "talking" to that person
• eaving for longer than 2 seconds gives a new ID
• rotating the phone works, IDs start fresh
• leaving and reopening the camera restarts at f1

TESTING

• swift test --package-path apps/ios/Packages/GraptionVision: 17 tests pass (moving faces, reordered detections, fast movers, 2 second dropout keeps ID, retirement after 2 seconds, no ID reuse, reset, forgetTracks, speaker guess)
• The 2 second dropout test fails with the old 1 second value, so it covers the bug found on device
• swift test on GraptionCore (P7): 7 tests pass
• App builds for iOS Simulator with CI flags

Video: (drag the screen recording here, 10 MB max)

NOTES FOR REVIEWERS

• Tradeoff: someone new stepping into the same spot within 2 seconds inherits the previous person's ID
• Tracker tuning (IoU 0.3, 1.5x face size) is from the spec
• swift test can't run on macOS for GraptionAudio and GraptionUI (iOS-only platform errors). This PR doesn't touch them
• Unrelated leftovers on main for a follow-up: committed face_landmarker.task weights, "Python on PACE" in section 3, stray root Package.swift and Tests/ (breaks the VSCode Swift extension)