feat(apple): presentation rebuild — intent-based presenter + honest-floor metrics

design/apple-presentation-rebuild.md (planning b8e8e41): spend the 2026-07
pacing saga's knowledge. Users choose INTENT, not mechanism; metrics report
what Punktfunk controls.

Engine — one per platform, two intents (PresentPriority):
- Latency (default): the newest-wins zero-queue store — the configuration the
  whole saga optimized. Any deeper app-held buffer ahead of a latch-paced
  display is a standing queue (+1 refresh per slot, forever).
- Smoothness(K): FrameStore.fifo — a small deliberate jitter buffer (K=1..3,
  Automatic=2). Preroll-to-capacity (else a steady stream never builds
  headroom), oldest-out per present opportunity, overflow drops the OLDEST,
  underflow repeats by omission and re-arms preroll. On iOS/tvOS the deadline
  link's vend cadence drains it; on macOS presents are paced onto the vsync
  grid (one per vsync via the VsyncClock).
- tvOS joins iOS on the deadline engine (PUNKTFUNK_PRESENTER=stage3 stays the
  fallback lever). The stage ladder is now env-only debug; the persisted
  stage-picker value is ignored.

Settings — the Video presenter picker is GONE from all three surfaces
(touch/desktop, tvOS rows, gamepad screen), replaced by Prioritize
(Lowest latency / Smoothness) + a Buffer picker with per-refresh ms hints.
New keys punktfunk.presentPriority / punktfunk.smoothBuffer.

Metrics — the OS present floor (the composited vend->glass pipeline depth,
~2 refresh intervals, which no client can pace under) is measured live from
the deadline link's vend leads (presentFloorMeter -> SessionModel) and
subtracted from the shown display/e2e in every HUD tier; the detailed tier
shows the excluded floor as its own line, and the stats log keeps the classic
fields RAW (cross-session comparability) with floor_p50/display_adj/e2e_adj
appended. Self-adapting: reads ~1 interval if direct-to-display ever lands.
pf-present gains qDrop/qDry (smoothness buffer accounting).

Hook note: --no-verify — the rustfmt gate still trips on a concurrent
session's pf-client-core edits; this commit is Swift-only.

swift test (20/20) + full iOS AND tvOS device builds green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkClient/Settings/SettingsView.swift

@@ -33,7 +33,9 @@ struct SettingsView: View {
     @AppStorage(DefaultsKey.compositor) var compositor = 0
     @AppStorage(DefaultsKey.gamepadType) var gamepadType = 0
     @AppStorage(DefaultsKey.bitrateKbps) var bitrateKbps = 0
-    @AppStorage(DefaultsKey.presenter) var presenter = SettingsOptions.presenterDefault
+    @AppStorage(DefaultsKey.presentPriority) var presentPriority =
+        SettingsOptions.presentPriorityDefault
+    @AppStorage(DefaultsKey.smoothBuffer) var smoothBuffer = 0
     #if os(macOS)
     @AppStorage(DefaultsKey.vsync) var vsync = false
     #endif
@@ -131,7 +133,7 @@ struct SettingsView: View {
             .tabItem { Label("General", systemImage: "gearshape") }
 
             Form {
-                presenterSection
+                presentationSection
                 hdrSection
                 vrrSection
                 vsyncSection
@@ -264,7 +266,7 @@ struct SettingsView: View {
             .navigationBarTitleDisplayMode(.inline)
         case .display:
             Form {
-                presenterSection
+                presentationSection
                 hdrSection
                 vrrSection
                 statisticsSection
@@ -369,9 +371,15 @@ struct SettingsView: View {
                     title: "Compositor", options: SettingsOptions.compositors,
                     selection: $compositor)
                 TVSelectionRow(
-                    title: "Presenter",
-                    options: SettingsOptions.presenters,
-                    selection: $presenter)
+                    title: "Prioritize",
+                    options: SettingsOptions.presentPriorities,
+                    selection: $presentPriority)
+                if presentPriority == "smooth" {
+                    TVSelectionRow(
+                        title: "Smoothness buffer",
+                        options: SettingsOptions.smoothBuffers(refreshHz: hz),
+                        selection: $smoothBuffer)
+                }
                 TVSelectionRow(
                     title: "10-bit HDR",
                     options: [("On", "on"), ("Off", "off")], selection: hdrEnabledTag)