chore: scaffold Kolmekivi from nih-plug-template

A stereo delay/echo plugin. Scaffolded rather than forked: the template
and the plugins built from it diverge on branding immediately, so they
share code by file copy — as codename-206 does — not by merge base. This
repo starts its own history.

Branded with tools/brand-plugin.sh. Everything derives from PLUGIN_NAME
("Kolmekivi" -> kolmekivi / Kolmekivi / KolmekiviParams), so no override
is pinned. CODENAME is set to the repo name and, by convention, stays
there even if the plugin is later renamed.

Two identity constants are now frozen and must never move, because hosts
key saved projects and presets off them:

    CLAP_ID        org.novoyuuparosk.kolmekivi
    VST3_CLASS_ID  KolmekiviDelay!!            (exactly 16 bytes)

Host categorisation is set for a delay rather than left at the template's
generic placeholders — ClapFeature::{AudioEffect,Delay,Stereo} and
Vst3SubCategory::{Fx,Delay}. These decide where the plugin appears in a
host's browser and are not covered by the branding checker, which knows
about names rather than categories.

The DSP is not written. src/lib.rs still carries the template's example
gain parameter, so the plugin builds, bundles and loads while the delay is
implemented.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WHt4DykxXaQnyaJfyS8KCn

NOTICE

@@ -0,0 +1,46 @@
+Kolmekivi
+Copyright 2026 Mikkeli Matlock
+
+This product is licensed under the GNU General Public License v3.0 or later.
+See LICENSE for the full terms.
+
+--------------------------------------------------------------------------------
+Third-party material
+--------------------------------------------------------------------------------
+
+Portions of src/lib.rs derive from the NIH-plug cookiecutter template and from
+NIH-plug's `gain` example plugin, both by Robbert van der Helm:
+
+    https://github.com/robbert-vdh/nih-plug-template
+    https://github.com/robbert-vdh/nih-plug
+
+Those portions are licensed under the ISC License:
+
+    ISC License
+
+    Copyright (c) 2022 Robbert van der Helm
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+    SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+    OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+    CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+ISC is GPL-compatible, so this notice is retained rather than superseded.
+
+--------------------------------------------------------------------------------
+Note on the `vst3` feature
+--------------------------------------------------------------------------------
+
+Building with `--features vst3` links `vst3-sys`, which is licensed GPLv3 or
+later. This is the reason a distributed VST3 build must be GPL-licensed. No
+Steinberg SDK source is vendored or redistributed by this project; "VST" is a
+trademark of Steinberg Media Technologies GmbH, and using it to describe a
+distributed product is governed by Steinberg's trademark terms, separately from
+any copyright licence above.