feat(rumble): host-authoritative self-terminating envelopes (0xCA v2)

Rumble was level-triggered, unbounded state on a lossy channel: a non-zero
level meant "buzz until further notice", healed only by the host re-sending
state every 500 ms, and every client guessed when the host had died with its own
magic timeout (SDL 1.5 s, Apple 1.6 s, Android up to 60 s). A lost stop, a
reordered start, or a dead host could drone the motor for seconds.

Make "stuck rumble" inexpressible on the wire. The 0xCA datagram grows a
length-tolerant tail — [u8 seq][u16 ttl_ms] — so it self-terminates: the host
authorizes a level for at most ttl_ms and renews it (~120 ms) while it holds,
letting an abandoned one lapse client-side. seq is a per-pad wrapping reorder
gate (reusing GamepadSnapshot::seq_newer) so a reordered stale start can't
re-light a stopped motor. Decoders read the first 7 bytes as a plain level and
ignore the tail, so no wire-version bump: an old client renders a new host's
levels, and a new client falls back to its prior staleness heuristic against an
old host (ttl = None). All four generation pairings render correctly.

- core: encode_rumble_datagram_v2 / decode_rumble_envelope (datagram.rs); the
  client demux applies the seq gate then forwards (pad, low, high, Option<ttl>);
  next_rumble is unchanged (drops ttl), next_rumble_ttl keeps it; ABI adds
  punktfunk_connection_next_rumble2 + PUNKTFUNK_RUMBLE_NO_TTL, ABI_VERSION 4->5
  (WIRE_VERSION unchanged — the tail is backward-compatible).
- host (punktfunk1.rs): the flat 500 ms refresh becomes a renewal loop that bumps
  seq + stamps a fresh TTL on active pads and drains a short post-stop zero burst,
  then goes quiet. Hatches: PUNKTFUNK_RUMBLE_ENVELOPE=0 (legacy v1 + flat refresh,
  a bisect switch), PUNKTFUNK_RUMBLE_TTL_MS (clamped [150, 5000]).
- renderers honor the TTL as their playback duration/deadline and keep their old
  heuristic only for a legacy (ttl=None) update: pf-client-core (the Deck haptic
  keep-alive is now deadline-bounded so it can't sustain a host-stopped rumble),
  clients/windows (SDL duration), android (JNI packs the lease out-of-band in bit
  48 so any u16 ttl is unambiguous; Kotlin createOneShot(ttl)), apple
  (RumbleRenderer.envelopeDeadline + nextRumble2; sessionStaleSeconds demoted to
  the legacy fallback).
- tests: codec round-trip + tail tolerance + seq-gate reorder (Rust); the probe
  asserts the v2 tail arrived under PUNKTFUNK_TEST_FEEDBACK; the Apple loopback
  asserts ttlMs round-trips end to end; RumbleTuning lease-decision cases.

The host-side idle-timeout from the previous commit is defense in depth on the
game side; this is the guarantee on the client side. Design:
punktfunk-planning/design/rumble-envelope-plan.md.

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

clients/android/native/src/feedback.rs

@@ -24,8 +24,12 @@ const TAG_PLAYER_LEDS: u8 = 0x02;
 const TAG_TRIGGER: u8 = 0x03;
 
 /// `NativeBridge.nativeNextRumble(handle): Long` — block up to ~100 ms for the next rumble update.
-/// Returns `(low << 16) | high` (each 0..=0xFFFF; `0` = stop), or `-1` on timeout / session closed.
-/// Pad index is dropped (single-pad model). Run from a dedicated Kotlin poll thread.
+/// Returns a packed positive long: bit 48 = "has a v2 lease", bits 32..47 = `ttl_ms`, bits 16..31 =
+/// `low`, bits 0..15 = `high` (`low`/`high` 0..=0xFFFF, `0/0` = stop). The lease flag is
+/// out-of-band so ANY 16-bit `ttl_ms` — including 0xFFFF — is unambiguous (no in-band sentinel to
+/// collide with a real 65535 ms lease). No lease (legacy host) → bit 48 clear, and Kotlin falls
+/// back to its long one-shot. `-1` on timeout / session closed (all packed values are positive, so
+/// `-1` stays unambiguous). Pad index is dropped (single-pad model). Run from a Kotlin poll thread.
 #[no_mangle]
 pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeNextRumble(
     _env: JNIEnv,
@@ -37,12 +41,20 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeNextRumble(
         if handle == 0 {
             return -1;
         }
-        // SAFETY: live handle per the nativeConnect/nativeClose contract; next_rumble is &self on the
-        // Sync connector — safe alongside the decode/audio/input threads. Kotlin stops these poll
+        // SAFETY: live handle per the nativeConnect/nativeClose contract; next_rumble_ttl is &self on
+        // the Sync connector — safe alongside the decode/audio/input threads. Kotlin stops these poll
         // threads (and joins them — unbounded) before nativeClose frees the handle.
         let h = unsafe { &*(handle as *const SessionHandle) };
-        match h.client.next_rumble(PULL_TIMEOUT) {
-            Ok((_pad, low, high)) => (jlong::from(low) << 16) | jlong::from(high),
+        match h.client.next_rumble_ttl(PULL_TIMEOUT) {
+            Ok((_pad, low, high, ttl)) => {
+                // The reorder gate already ran in the core, so this update is fresh. Encode the
+                // Option out-of-band: a real lease sets bit 48 and carries ttl_ms verbatim.
+                let (lease_flag, ttl_bits) = match ttl {
+                    Some(ms) => (1i64 << 48, jlong::from(ms) << 32),
+                    None => (0, 0),
+                };
+                lease_flag | ttl_bits | (jlong::from(low) << 16) | jlong::from(high)
+            }
             Err(_) => -1, // NoFrame (timeout) or Closed — Kotlin loops on its running flag
         }
     })