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/Cargo.toml

@@ -2,7 +2,7 @@
 name = "hack-house"
 version = "0.1.0"
 edition = "2021"
-description = "hack-house — encrypted collaborative sessions with a summoned sandbox. ⛧"
+description = "hack-house — encrypted collaborative sessions with a summoned sandbox."
 license = "MIT"
 
 [[bin]]
@@ -34,7 +34,7 @@ vt100 = "0.15"
 tar = "0.4"
 
 # async + tui
-tokio = { version = "1", features = ["rt-multi-thread", "macros", "net", "io-util", "sync", "time"] }
+tokio = { version = "1", features = ["rt-multi-thread", "macros", "net", "io-util", "sync", "time", "signal"] }
 tokio-tungstenite = { version = "0.24", features = ["rustls-tls-webpki-roots"] }
 futures-util = "0.3"
 ratatui = { version = "0.29", features = ["serde", "unstable-rendered-line-info"] }