chore(maestro): drop obsolete web/dist/.gitkeep handling

build.rs now builds web/dist before include_dir! evaluates, so the
checked-in .gitkeep placeholder is no longer needed for a fresh checkout
to compile (verified by building with web/dist entirely absent). Ignore
dist/ wholesale and update the static_bundle doc comment.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/.gitignore

@@ -1,5 +1,4 @@
 node_modules/
-dist/*
-!dist/.gitkeep
+dist/
 *.log
 *.tsbuildinfo