feat(shell): add scrollback history capture on shell exit

- Add smart_exit function: captures Kitty scrollback to a timestamped
  log file on exit; --no-log/-n skips capture; auto-prunes oldest logs
  once count exceeds SCROLLBACK_HISTORY_MAX_FILES
- Wire exit → smart_exit in config.fish for interactive sessions;
  export SCROLLBACK_HISTORY_DIR and SCROLLBACK_HISTORY_MAX_FILES with
  sane defaults (~/.terminal_history and 100 respectively)
- Update cat to detect files in SCROLLBACK_HISTORY_DIR or containing
  raw ANSI escape sequences and pass them through command cat instead
  of bat, preserving color output
- Remove redundant alias rm="rm -i" from tricks.fish (superseded by
  functions/rm.fish trash-aware wrapper)
- Sync README: new Scrollback History integration section, smart_exit
  added to System functions table, cat description updated, stale rm
  Safety Wrapper entry and note removed

conf.d/tricks.fish

@@ -96,7 +96,6 @@ alias egrep='egrep --color=auto'
 # Safety aliases (Confirmation before overwriting/deleting)
 alias cp="cp -i"
 alias mv="mv -i"
-alias rm="rm -i"
 
 # Archives and networking short-hands
 alias tarnow='tar -acf '