feat(hh): graceful shutdown, crypt default theme, neutralize branding, share-prep

- Graceful shutdown: Ctrl+C quits in chat (interrupts PTY while driving),
  RAII TermGuard + panic hook + SIGTERM/SIGHUP always restore the terminal
- Default theme is now "crypt" (neutral monochrome); theme sigil mirrored in
  chat/roster/help so the pentagram only renders under the "church" theme
- Neutralize inverted-pentagram branding across CLI, scripts, docs, and Cargo
  metadata (kept only in themes/church.toml + the render-time placeholder)
- Rewrite root README around hack-house; add bootstrap.sh, SECURITY.md,
  CODE_OF_CONDUCT.md, CHANGELOG.md, and issue/PR templates
- .gitignore cleanup; stop tracking .venv

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hh/smoke.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# hack-house smoke test ⛧
+# hack-house smoke test
 # Exercises the full use-case path end to end against a live server:
 #   rust unit tests → SRP self-test → boot server → rust client handshake +
 #   round-trip → cross-language (python decrypts what the rust client sent).
@@ -74,4 +74,4 @@ asyncio.run(main())
 PYEOF
 
 echo
-echo "✓ SMOKE PASS — crypto · SRP · fernet · cross-language relay all green ⛧"
+echo "✓ SMOKE PASS — crypto · SRP · fernet · cross-language relay all green"