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>

.gitignore

@@ -1,18 +1,25 @@
-/__pycache__/
-/i-try/
-/venv/
-test_rsa.py
-.gitignore
-commiter.py
-__pycache__
+# Python
+__pycache__/
 *.pyc
-.idea
+/venv/
+.venv/
+.pytest_cache/
+.benchmarks/
+build/
+dist/
+*.egg-info/
+cmd_chat.egg-info/
+secured_console_chat.egg-info/
+
+# Secrets / keys
 *.pem
-__pycache__
-cmd_chat.egg-info
-build
-dist
+
+# Editor / OS
+.idea/
+
+# Project scratch
+/i-try/
+test_rsa.py
+commiter.py
 true.txt
-secured_console_chat.egg-info
-.pytest_cache//.venv/
 /downloads/