zip-doc audit: last stale key claim + a keylight-stub warning at cut time

Full audit of every user-facing artifact in a freshly cut zip (33 checks, all
passing -- README substitutions/controls/migration story, CONTROLS.txt ASCII
flatten, CONTROLS.html loader + wrap, launchers byte-identical, exe carries the
migration):

  * README's intro still said 'Press V any time to toggle the external camera'
    -- the one key claim outside the rewritten controls block, stale for every
    fresh/migrated install since the board took V.  Backtick now.
  * mkdist warns at cut time when the exe carries the KEYLIGHT STUB (build
    machine's SDK < 10.0.22000), because the README promises the RGB feature
    -- nobody should ship a stub build believing that promise ships with it.

The audit zip itself was deleted after verification: its version stamp predates
today's doc commits, and a release cut should rebuild the exe at final HEAD
first (the 554 procedure).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tools/mkdist.py

@@ -75,6 +75,22 @@ def main():
     zpath = os.path.join(outdir, name + ".zip")
 
     exes = ["build/Release/btl4.exe"]
+
+    # HONESTY CHECK (2026-07-26): the RGB keylight compiles to a dormant stub
+    # on machines whose Windows SDK is too old (< 10.0.22000 -- see
+    # CMakeLists), and the README promises the feature.  Say so at cut time,
+    # so nobody ships a stub build believing the promise.
+    try:
+        with open(exes[0], "rb") as f:
+            if b"built without Dynamic Lighting support" in f.read():
+                print("  *** NOTE: this exe carries the KEYLIGHT STUB (build "
+                      "machine's SDK too old).  The README's RGB-keyboard "
+                      "feature will be dormant in this zip -- build on a "
+                      "machine with SDK >= 10.0.22000 to ship the real "
+                      "mirror. ***")
+    except OSError:
+        pass
+
     bats = ["players/play_solo.bat", "players/join.bat", "players/join_lan.bat",
             "players/joyconfig.bat"]
     if steam_on: