refactor(bridge): split fx bridge, stabilize VST3 host chain, drop old install engines

- remove diagnostic canaries from audio hot path (crackle fix) and
  stuck C5 note raw-MIDI test (Vst2Instrument::init noteOff)
- split native bridge into daw_vst_bridge (VSTi) + fx_vst_bridge (VST FX)
- VST3: processData prepare before setActive, zero input buses, accept
  both .vstpreset and bridge-state blob in RenderJob presets
- native_render/vst_engine: bridge-exe discovery + render_fx_chain + /fx-gui
- delete old install/ engine binaries (install via sidecar+resources now)
- add BUILD_LAYOUT.md, build_selfcheck, tools/ diagnostics

tools/walk_stack.py

@@ -0,0 +1,69 @@
+import struct
+
+path = r"C:/Users/locpham/AppData/Local/Temp/sf_dumps/bridge_crash_1696.dmp"
+data = open(path, "rb").read()
+sig, ver, numstreams, sdir = struct.unpack_from("<IIIIIIQ", data, 0)[:4]
+streams = {}
+for i in range(numstreams):
+    stype, datasize, rva = struct.unpack_from("<III", data, sdir + i * 12)
+    streams[stype] = (rva, datasize)
+
+mods = []
+rva, sz = streams[4]
+n = struct.unpack_from("<I", data, rva)[0]
+pos = rva + 4
+for i in range(n):
+    base, imgsz, cksum, ts, name_rva = struct.unpack_from("<QIIII", data, pos)
+    nlen = struct.unpack_from("<I", data, name_rva)[0]
+    name = data[name_rva + 4:name_rva + 4 + nlen].decode("utf-16-le", "replace").rstrip("\x00")
+    mods.append((base, imgsz, name))
+    pos += 108
+
+def mod_for(addr):
+    for base, szz, name in mods:
+        if base <= addr < base + szz:
+            return base, name.split("\\")[-1]
+    return None, None
+
+# crash thread context
+rva, sz = streams[6]
+ex_tid = struct.unpack_from("<I", data, rva)[0]
+rva, sz = streams[3]
+n = struct.unpack_from("<I", data, rva)[0]
+pos = rva + 4
+ctx_rva = None
+for i in range(n):
+    tid2, susp, pric, pri, teb, st_start, st_sz, st_rva, ctx_sz2, ctx_rva2 = struct.unpack_from("<IIIIQQIIII", data, pos)
+    if tid2 == ex_tid:
+        ctx_rva = ctx_rva2
+        st_rva_used = st_rva
+        st_start_used = st_start
+    pos += 48
+rip = struct.unpack_from("<Q", data, ctx_rva + 0xF8)[0]
+rsp = struct.unpack_from("<Q", data, ctx_rva + 0x98)[0]
+print("crash tid", ex_tid, "RIP", hex(rip), "RSP", hex(rsp))
+
+# find memory region covering RSP
+rva, sz = streams[5]
+n = struct.unpack_from("<I", data, rva)[0]
+pos = rva + 4
+region = None
+for i in range(n):
+    start, msz, mrva = struct.unpack_from("<QII", data, pos)
+    if start <= rsp < start + msz:
+        region = (start, msz, mrva)
+    pos += 16
+print("stack region", region and (hex(region[0]), hex(region[1])))
+
+# walk stack: assume return addresses are qwords that fall into executable modules
+start, msz, mrva = region
+base_rsp = rsp
+print("\nstack walk from RSP:")
+prev = None
+for j in range(0, 16384 - 8, 8):
+    addr = base_rsp + j
+    if addr >= start + msz: break
+    val = struct.unpack_from("<Q", data, mrva + (addr - start))[0]
+    b, nm = mod_for(val)
+    if nm and (val - b) > 0x1000:  # code pointer heuristic (offset beyond header)
+        print("  %016x  [%04x]  %016x -> %s+%x" % (addr, j, val, nm, val - b))