feat: drive NQC through Phase 1-4 — tests, spec, ABI/FFI, polish

Phase 1 — 128 unit tests across database, formatter, client, and main
module. Promoted key utility functions to pub for testability.

Phase 2 — EBNF grammar (spec/grammar.ebnf) covering meta-commands,
protocol wire format, CLI arguments, and output formatting. Formal
specification (spec/SPEC.core.scm) defining type system, protocol
invariants, registry semantics, and correctness guarantees. 19
conformance tests verifying spec invariants.

Phase 3 — Idris2 ABI with dependent type proofs for ports, non-empty
strings, URL paths, format roundtrip, and memory layout alignment.
Zig FFI (32 tests) implementing CSV escape, semicolon stripping, URL
construction, query body building, and status classification.

Phase 4 — Custom profile JSON loading from nqc-profiles.json. Persistent
query history (~/.nqc_history) with search. In-memory LRU query cache
with mutation bypass. ANSI keyword highlighting. New meta-commands:
\history, \search, \clearcache. 43 additional tests.

Total: 190 Gleam + 32 Zig = 222 tests, all passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

nqc/.gitignore

@@ -2,3 +2,7 @@
 *.ez
 /build
 erl_crash.dump
+
+# Zig build artifacts
+ffi/zig/.zig-cache/
+ffi/zig/zig-out/

nqc/ffi/zig/build.zig

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: PMPL-1.0-or-later
+// Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+//
+// build.zig — Build configuration for the NQC Zig FFI library (Zig 0.15.2).
+
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    // --- Library module for import ---
+    const nqc_mod = b.addModule("nqc_ffi", .{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // --- Unit tests ---
+    const unit_test_mod = b.createModule(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    const unit_tests = b.addTest(.{
+        .root_module = unit_test_mod,
+    });
+    const run_unit_tests = b.addRunArtifact(unit_tests);
+
+    // --- Integration tests ---
+    const integration_test_mod = b.createModule(.{
+        .root_source_file = b.path("test/integration_test.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    integration_test_mod.addImport("nqc_ffi", nqc_mod);
+    const integration_tests = b.addTest(.{
+        .root_module = integration_test_mod,
+    });
+    const run_integration_tests = b.addRunArtifact(integration_tests);
+
+    // --- Test step ---
+    const test_step = b.step("test", "Run unit and integration tests");
+    test_step.dependOn(&run_unit_tests.step);
+    test_step.dependOn(&run_integration_tests.step);
+}