feat(vst): S18 VST3 channel isolation — beta ReaSampler 9000 pairs with beta extension only

Fork the VST3 class UID (beta UID minted+frozen), on-disk name, and display
name by the one channel bit via app_version; couple UID selection to the
channel at compile time so a refactor can't split identity from data.

src/vst/reasampler_vst.h

@@ -2,41 +2,78 @@
 // (Phase S). One place for the plugin's class UID, name, vendor, and version so the
 // processor, factory, and editor agree.
 //
-// The class UID is FOREVER-STABLE once shipped: a REAPER project that instantiates this
-// instrument records the UID, so changing it orphans every saved instance. Minted once
-// for the spike; do not regenerate.
+// A class UID is FOREVER-STABLE once shipped: a REAPER project that instantiates this
+// instrument records the UID, so changing it orphans every saved instance. Minted once;
+// do not regenerate.
+//
+// CHANNEL ISOLATION (S18, beta-in-isolation — the instrument-side companion to V4). Just
+// as V4 gave the extension a per-channel ext-state namespace / command-id family / dock
+// ident, S18 gives the VST3 instrument a per-channel PLUGIN IDENTITY: its class UID, its
+// on-disk filename, and its display name all fork by the ONE channel bit
+// (REASAMPLER_CHANNEL_IS_BETA, from version_generated.h). ONE class per binary — the bit
+// selects which UID compiles into the single DEF_CLASS2, so a beta build carries only the
+// beta identity and can never present the stable one (mirrors V4's fully-isolated-binary
+// philosophy). The two UIDs below are BOTH frozen forever; the filename + display name
+// derive from app_version's vstOutputName()/vstPluginName() (this header owns only the
+// binary UID identity — the string identity lives in the pure module).
 
 #pragma once
 
 #include "pluginterfaces/base/funknown.h"
 
+#include "version_generated.h"  // REASAMPLER_CHANNEL_IS_BETA — the one channel bit
+
 namespace reasampler::vst {
 
-// Human-facing identity (S-NAME-1, SETTLED 2026-07-26). "ReaSampler" is the extension
-// (capture + organization); the MIDI-playback instrument's product name is
-// "ReaSampler 9000" — the string that surfaces in REAPER's FX browser, the factory
-// display name, the editor title band, and the embed-strip label. The on-disk module is
-// renamed to match (CMake OUTPUT_NAME reasampler_9000.vst3). The VST3 class UID below is
-// the compat anchor and is NOT changed by the rename — a saved REAPER project rebinds a
-// saved instance by class UID, so the display/filename rename keeps existing instances
-// resolving (compat is a DAW-verify; see PLAN.md §S-NAME-1).
-inline constexpr const char* kPluginName = "ReaSampler 9000";
+// Vendor identity (S-NAME-1, SETTLED 2026-07-26). Shared across channels — V4 kept the
+// lane-name prefix shared, so shared-where-V4-shares is the default (the channel is carried
+// by the UID + filename + display fork, not the vendor block).
 inline constexpr const char* kVendorName = "ReaSampler";
 inline constexpr const char* kVendorUrl = "https://github.com/daniel-c-harvey/reasampler";
 inline constexpr const char* kVendorEmail = "mailto:the.real.daniel.harvey@gmail.com";
 
-// The processor class UID (the SingleComponentEffect). FOREVER-STABLE once shipped —
-// a saved REAPER project records it, so changing it orphans every saved instance.
-// Minted once for the S1 spike (2026-07-26). Defined as four longs so the factory's
-// INLINE_UID (compile-time brace init) and the runtime FUID below share one source.
+// -----------------------------------------------------------------------------------------
+// The two FOREVER-FROZEN VST3 class UIDs — one per channel. A saved REAPER project records
+// the UID of the instance it instantiated and rebinds by it on reopen, so EACH is a
+// permanent commitment: changing either orphans every saved instance of that channel. The
+// channel bit selects which one this binary's factory registers (below) — one class per
+// binary, never both. Documented with the SAME gravity: neither may EVER be regenerated.
+
+// STABLE class UID (S-NAME-1). Minted at the S1 spike (2026-07-26), locked. FROZEN FOREVER.
 #define REASAMPLER_PROC_UID_1 0x5E45A11E
 #define REASAMPLER_PROC_UID_2 0x9C7B4D6A
 #define REASAMPLER_PROC_UID_3 0xB1E3F208
 #define REASAMPLER_PROC_UID_4 0x4A6C1D9F
 
-static const Steinberg::FUID kReaSamplerProcessorUID(REASAMPLER_PROC_UID_1,
-                                                     REASAMPLER_PROC_UID_2,
-                                                     REASAMPLER_PROC_UID_3,
-                                                     REASAMPLER_PROC_UID_4);
+// BETA class UID (S18). Minted once (2026-07-26), locked FROM THIS WAVE per Daniel's
+// fast-track (fork S18-F1: mint now, not at first beta release). FROZEN FOREVER — the same
+// permanent lock as the stable UID; do not regenerate even though no beta VST has shipped.
+#define REASAMPLER_PROC_UID_BETA_1 0xCCFFEB3A
+#define REASAMPLER_PROC_UID_BETA_2 0x4FF532A6
+#define REASAMPLER_PROC_UID_BETA_3 0x9E181798
+#define REASAMPLER_PROC_UID_BETA_4 0x4256955F
+
+// The channel-selected UID macros the factory's INLINE_UID (compile-time brace init) and the
+// runtime FUID below both source, so exactly one class UID is compiled into this binary. This
+// is the ONLY channel #ifdef in the VST shell (an INLINE_UID needs literal brace-init tokens,
+// so it cannot route through app_version's runtime string accessors — the header owns the
+// binary UID fork, app_version owns the string fork).
+#if REASAMPLER_CHANNEL_IS_BETA
+#define REASAMPLER_ACTIVE_UID_1 REASAMPLER_PROC_UID_BETA_1
+#define REASAMPLER_ACTIVE_UID_2 REASAMPLER_PROC_UID_BETA_2
+#define REASAMPLER_ACTIVE_UID_3 REASAMPLER_PROC_UID_BETA_3
+#define REASAMPLER_ACTIVE_UID_4 REASAMPLER_PROC_UID_BETA_4
+#else
+#define REASAMPLER_ACTIVE_UID_1 REASAMPLER_PROC_UID_1
+#define REASAMPLER_ACTIVE_UID_2 REASAMPLER_PROC_UID_2
+#define REASAMPLER_ACTIVE_UID_3 REASAMPLER_PROC_UID_3
+#define REASAMPLER_ACTIVE_UID_4 REASAMPLER_PROC_UID_4
+#endif
+
+// The runtime FUID for the class this binary registers — the channel-selected UID above.
+static const Steinberg::FUID kReaSamplerProcessorUID(REASAMPLER_ACTIVE_UID_1,
+                                                     REASAMPLER_ACTIVE_UID_2,
+                                                     REASAMPLER_ACTIVE_UID_3,
+                                                     REASAMPLER_ACTIVE_UID_4);
 
 }  // namespace reasampler::vst