v0.32.0

### Added

- **Reversible (server-arbitrated) barge-in** —
  `[bridge.barge_in].mode = "pause"`
  (`docs/design/DESIGN_REVERSIBLE_BARGE_IN.md`; #285/#286). Today a
  cough, laugh, or backchannel ("uh-huh") that trips VAD irreversibly
  kills the bot's playout. Pause mode reacts instantly but
  *reversibly*: playout is flushed within one frame — exactly like
  `auto_clear` — but the unplayed tail is retained, and the WS server
  (the only layer with STT) rules on intent:
  - `speech_started` carries `decision_pending: true` +
    `decision_deadline_ms` when an arbitration arms;
  - the server answers **`barge_in_confirm`** (real interruption —
    tail dropped) or **`barge_in_reject`** (false positive — playout
    resumes mid-utterance); a `clear` during the window acts as
    confirm, and late verdicts are harmless no-ops;
  - every resolution is acknowledged with
    **`barge_in_resolved { outcome: confirmed | rejected | timeout }`**;
  - no verdict within `decision_ms` (default 500) applies
    `on_timeout` (default `confirm` — a server that never rules
    degrades safely to "auto_clear delayed by the window");
  - `resume_max_secs` (default 30) caps the retained audio;
  - `start.barge_in_mode` announces the call's resolved policy;
  - per-route overrides via `[route.bridge.barge_in]`, field-wise;
  - the existing `debounce_ms` echo gate composes in front (acoustic
    filter first, semantic arbitration second).
  Arbitration only arms while the bot is playing, is suspended in
  conference rooms, and resolves as confirm when preempted by
  mute/hold/park/announce/room-join or a WS drop. Off by default;
  protocol stays **v1** (all additions additive), CDR stays **v4**
  (additive optional `quality` counters).
- **Server SDKs**: typed `BargeInResolved` / extended `SpeechStarted`
  and `Start`, plus `barge_in_confirm()` / `barge_in_reject()` (Python)
  and `bargeInConfirm()` / `bargeInReject()` (TypeScript). The echo
  reference servers answer arbitration requests with a reject by
  default (`SIPHON_ECHO_BARGE_IN_VERDICT=confirm` flips it).
- **Conformance**: new bundled `barge-in-pause` testkit scenario
  (verdict within the deadline + timeout-outcome tolerance) and a
  `session.barge_in_mode` scenario option.
- **Metrics**: `siphon_ai_barge_in_decisions_total{outcome}` and
  `siphon_ai_barge_in_decision_seconds` (explicit 50 ms–5 s buckets).
- **SIPp harness**: `barge_in_pause` phase with *real caller media* —
  a run-time-generated G.711 tone pcap (`gen_tone_pcap.py`, stdlib
  only) replayed via `play_pcap_audio`, driving VAD → pause →
  reject → resume end-to-end. The suite is now 36 scenarios.

### Fixed

- Route-level `[route.bridge.barge_in]` strings are now **validated at
  config load** — previously a typo'd route `mode` was silently inert
  (the runtime merge skipped unparseable values).

---

**Artifacts**

- Static musl binaries for `x86_64` and `aarch64` (`.tar.gz`).
- Debian packages (`.deb`) for `amd64` and `arm64` — `apt install ./siphon-ai_*_amd64.deb`.
- `SHA256SUMS` — verify with `sha256sum -c SHA256SUMS`.
- `*-sbom.cdx.json` — CycloneDX SBOM.
- `SHA256SUMS.cosign.bundle` — cosign keyless signature over the checksums.
- Container: `ghcr.io/thevoiceguy/siphon-ai:v0.32.0` (multi-arch, cosign-signed).

Verify the checksums signature:
```
cosign verify-blob --bundle SHA256SUMS.cosign.bundle \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com \
  --certificate-identity-regexp 'release.yml@' SHA256SUMS
```