Reduce code-health debt: Swift format, dedupe, coverage (#26)

[sarthakagrawal927]

Progress on #26 (does not close it).

What changed

• Swift formatting. Adds .swift-format with the Fleet Swift convention already used by pace, live and significanthobbies (4 spaces, 120 columns, keep existing line breaks), then applies swift-format format. The changes are whitespace, line breaks, and semicolon and multi-declaration splits only. The ratchet now passes --configuration .swift-format explicitly.
  • Measured against the old implicit default (2 spaces, 100 columns), main has 4,553 diagnostics. Against the adopted config, main has 363 before formatting and 8 after.
  • The 8 left are lint-only: 7 SCREAMING_CASE constants, which are kept because they mirror protocol.ts and dev config, and 1 @retroactive Identifiable on URL.
• Swift refactors (behavior-preserving).
  • Split CompositeExporter.export (parked v2) from 180 lines to 97 by extracting helpers for head-trim, the camera-inset transform, the video composition, the timeline and the export session.
  • Moved the add-only Photos save into a shared PhotosVideoSaver, used by ScreenRecorder (v1) and RecordingController (parked v2). Messages, add-only permission and state transitions are unchanged.
  • Dropped one unused SwiftUI environment read.
• TypeScript duplication. Moved the shared score-HUD preamble and hand-joint lookup into games/canvas-utils, which removes all 3 TS clone groups.
• Tests (no snapshots). Covers:
  • the relay server: join/role enforcement, presence, direction-gated relay, ping/pong, pose rate limit, send-after-close
  • the native JS bridge
  • the keyboard debug controller
  • canvas helpers
  • the update logic of Reach & Dodge, Slice and Motion Maker, made deterministic by mocking Math.random

Ratchets (before → after)

Gate	Before	After
Coverage lines / branches / functions / statements	6.43 / 10.12 / 7.01 / 6.53 %	39.46 / 37.76 / 43.55 / 39.95 % (min set to 39.4 / 37.7 / 43.5 / 39.9)
Complexity violations / max length	3 / 180	2 / 149
Duplication groups / lines	5 / 65	0 / 0
Swift-format diagnostics	4,553	8
Periphery findings	68	66

Checks

• pnpm check passes: 17 files, 82 tests, format/lint/typecheck/build, plus the coverage, unused, complexity, duplication, cycles, dependency (0 critical/high), suppression and hygiene gates.
• Local unsigned simulator build (xcodegen generate && pod install --deployment + xcodebuild ... CODE_SIGNING_ALLOWED=NO build) succeeds. pnpm quality:swift passes with MOTION_INDEX_STORE set (Periphery 3.8.0).

Not done (still on #26)

• The 2 remaining complexity violations are in PoseEstimator (buildAndEmit, computeHands). That is the live v1 Vision hot path, so I left it until it can be checked on a device.
• PartyKit's esbuild 0.21.5 moderate advisory.
• iOS test target.
• The other 66 Periphery findings. Most are parked-v2 recording/protocol-mirror code, which is kept on purpose.
• Camera/ReplayKit verification on a physical device.

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