Slash commands (/quit, /help) + zero compiler warnings

1. /quit and /help commands restored:
   - /quit: exits the interactive loop
   - /help: shows formatted help box with available commands & tips
   - Unknown commands get a friendly error pointing to /help
   - Slash commands intercepted before LLM processing (no token waste)

2. Zero warnings across entire workspace (13 files fixed):
   - Fixed ambiguous glob re-exports in gyandoot-core
   - Added #[allow(dead_code)] on intentional dead fields
   - Fixed unused imports, variables, and macros
   - Fixed unused assignments in subagents
   - cleaned up service.rs, profile, kanban warnings

install.sh now produces a completely clean build with zero warnings.

crates/gyandoot-profile/src/lib.rs

@@ -441,7 +441,7 @@ impl ConfigResolver {
             let default_path = self.default_config_path();
             if default_path.exists() {
                 match Self::load_profile_from_file(&default_path) {
-                    Ok(mut profile) => {
+                    Ok(profile) => {
                         if profile_name.is_empty() {
                             profile_name = profile.name.clone();
                         }