docs(adr): mark 0018 (Calcite adapter) Accepted — implemented on main

The calcite/ module (VortexSchema/Table/Aggregates + push-down rule) is built
and tested on main; the decision is adopted, so Status moves Proposed → Accepted.
Refresh the stale 'prototype branch' wording to point at the landed module.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

docs/adr/0018-calcite-sql-adapter.md

@@ -1,6 +1,7 @@
 # ADR 0018: Apache Calcite SQL adapter — be a push-down source, not an engine
 
-- **Status:** Proposed
+- **Status:** Accepted — Phases 0–2 (schema/scan, filter + projection push-down, MIN/MAX/COUNT
+  aggregate push-down) implemented in the `calcite/` module; SUM/AVG push-down pending
 - **Date:** 2026-06-24
 - **Deciders:** project maintainer
 - **Supersedes:** —
@@ -98,7 +99,7 @@ Phased productionisation:
   `MIN`/`MAX`/`COUNT` work now; `SUM`/`AVG` need the writer to emit a per-zone `SUM` stat first
   (ADR 0013 §6 — the same increment that also wants `NULL_COUNT`).
 
-### Prototype status (branch `feat/vortex-calcite-demo`)
+### Implementation status (landed in the `calcite/` module)
 
 Phases 0–2 are implemented and tested:
 

docs/adr/ADR.md

@@ -32,4 +32,4 @@ the decision shipped in (blank = not yet shipped).
 | 0015 | Drop Materialized fallbacks once Lazy has shipped | Accepted | 0.8.0 |
 | 0016 | vortex-arrow bridge module for Arrow interop  | Proposed  |          |
 | 0017 | In-house FlatBuffers codegen + MemorySegment runtime | Accepted  |          |
-| 0018 | Apache Calcite SQL adapter — push-down source | Proposed  |          |
+| 0018 | Apache Calcite SQL adapter — push-down source | Accepted  |          |