chore: repo declutter — remove report/backup junk; plan shorter top-level (#489)

* chore: remove tracked report/backup junk from repo

- scanner-qa-report.html (root, generated, unreferenced) — also de-clutters the
  top-level listing so the README surfaces sooner.
- specs/005-.../tasks.md.bak (editor backup)
- specs/044-.../test-report.html (generated report)

* chore: delete spec execution_log.md residue; gitignore *.bak + execution_log.md

Author: Dumbris

.gitignore

@@ -158,3 +158,7 @@ native/macos/MCPProxy/.build/
 
 # demo pipeline: playwright node_modules symlink (recreated at capture time)
 scripts/demo/node_modules
+
+# Transient work artifacts (brainstorm logs, editor backups)
+*.bak
+**/execution_log.md