docs: ratify vision revision across README/ARCHITECTURE/PORT_PLAN + ADRs 0002-0006

Folds the 2026-06-26 vision-revision pressure-test into the canonical
docs. The spec moves from Proposed to Ratified; the decisions it produced
land in the docs it said it would amend, with ADRs recording each
load-bearing reversal.

- README.md: reframe north star (AI-era contact-center engine, not
  Asterisk successor); persona; revised pillars (add data-ownership,
  demote WASM, promote spend-control); update 'what it is/isn't'.
- ARCHITECTURE.md: replace three-plane framing with fused per-call
  vertical + composable horizontal platform; remove control<->media
  hot-path gRPC hop; make the agent tap the central interface; add
  DX spine + GUI-as-API-client + k8s declarative/operational model.
  Also: 'too slow to police' -> 'too slow to enforce' (terminology).
- PORT_PLAN.md: recharacterize as capability checklist (not template);
  graduate contact-center capabilities to first-class domain; Rust-native
  trunk SIP rows; WASM demoted; thin-slice + capability ladder phasing.
- ADR-0001: marked Superseded by ADR-0003.
- ADR-0002 (new): north star + fused per-call core.
- ADR-0003 (new): Rust-native trunk SIP, no SBC shield.
- ADR-0004 (new): GPL-3.0-or-later license.
- ADR-0005 (new): Valkey as event bus + state store.
- ADR-0006 (new): WebRTC-first ingress; SIP endpoint deferred.
- vision-revision spec: status -> Ratified 2026-06-26.

docs/adr/0003-sip-rust-native-trunk.md

@@ -0,0 +1,76 @@
+# ADR-0003 — SIP strategy: Rust-native trunk SIP, no SBC shield
+
+- **Status:** Accepted
+- **Date:** 2026-06
+- **Supersedes:** [ADR-0001](0001-sip-strategy.md)
+- **Origin:** [vision-revision](../superpowers/specs/2026-06-26-vision-revision-design.md) §5
+
+## Context
+
+ADR-0001 layered the SIP strategy: own the Rust parser, but front the public edge with a
+proven **Kamailio + rtpengine** SBC to rent the "20-year device/carrier interop tail." That tail
+is real for a generic PBX — thousands of desk-phone quirks, NAT behaviors, carrier glare.
+
+Reconsidered under the AI-era contact-center scope ([ADR-0002](0002-north-star-and-fused-core.md)),
+the tail **collapses**: rutster talks to a few **documented, cooperative SIP-trunk providers
+(Telnyx, Bandwidth, Twilio SIP)**, IP-allowlisted, not thousands of far-end desk-phone UAs. An
+inbound/outbound SIP-trunk client against cooperative carriers is tractable in `rsip` / `ezk`,
+bounded by carrier documentation, not device quirks.
+
+The C SBC shield, meanwhile, directly contradicts the wedge:
+
+- It puts **C at the most-exposed seam** (the public internet) — gutting the memory-safety
+  headline *at the one place it matters most*.
+- It **terminates media twice** — rtpengine at the edge, rutster's media plane inside —
+  breaking "terminate media once" / "one auditable boundary."
+
+## Decision
+
+Own trunk SIP **and** media termination directly in the Rust core; IP-allowlist the handful of
+trunk providers. **No Kamailio + rtpengine shield. No pjproject FFI.**
+
+- Parser: `rsip` (message types/parsing). Sans-IO transaction/dialog/core: the `ezk` family.
+  No hostile bytes ever hit a C parser. **Fuzzed.**
+- The memory-safety thesis becomes **literally true at the wire**: hostile bytes hit a fuzzed
+  Rust parser first, at the edge of *our* trust boundary.
+- Interop surface is **bounded by carrier docs** (a finite, knowable set), not the unbounded
+  device tail ADR-0001 rented the shield for.
+
+### Scope boundary — this ADR is about *trunk* SIP, not *endpoint* SIP
+
+Inbound SIP **endpoint** registration (desk/soft phones: `REGISTER`, BLF/MWI, DTMF variants,
+per-device NAT/provisioning) is a **different axis** and is **deferred** — it re-imports the
+unbounded device-interop tail this ADR deliberately closes. Human-participant ingress is
+**WebRTC**. See [ADR-0006](0006-ingress-posture.md).
+
+## Topology
+
+```
+  hostile internet              trusted core
+  ───────────────►  (carrier trunk)  ──►  rutster control + media plane
+   (SIP trunks,                              (native Rust SIP parser +
+    far-end UAs)                               transaction/dialog core,
+                                               owned end-to-end here)
+```
+
+WebRTC ingress ships **first** and is unaffected (WebRTC signaling is app-defined, not SIP), so
+first-call never blocks on SIP.
+
+## Consequences
+
+- **Positive:** memory-safety headline *literally true* at the wire; one media-termination point;
+  no C operational dependency (no Kamailio/rtpengine config/deploy/expertise); no pjproject
+  license/threading/`unsafe` entanglement; the trunk client is bounded by carrier docs, not device
+  quirks.
+- **Negative / cost:** we own a (bounded) SIP-trunk client early; carrier-specific interop must be
+  maintained as trunks are added.
+- **Mitigation:** WebRTC-first ordering means first-call doesn't block on SIP; the thin-slice
+  steps 1–4 (media core → tap → brain → barge-in) all land before step 5 (real PSTN trunk).
+- **Graduation:** unlike ADR-0001, there is no shield to retire — the question is only how the
+  trunk client matures in production.
+
+## References
+
+- [ADR-0001](0001-sip-strategy.md) — superseded (the layered Kamailio+rtpengine + Rust-core plan)
+- [ADR-0002](0002-north-star-and-fused-core.md) — the fused-vertical reframe this SIP decision enables
+- [ADR-0006](0006-ingress-posture.md) — WebRTC-first ingress; SIP endpoint deferred