fix(bashrc): add ~/.local/bin to PATH in deployed bashrc

The bin/ scripts and pipx CLIs land in ~/.local/bin, which was not on
PATH in either deployed bashrc. Add an idempotent PATH guard to
bashrc-linux and bashrc-osx so dt, claude-provider, pymupdf, etc. are
found after login. Update the install.sh and README notes to match.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

bash/bashrc-linux

@@ -7,6 +7,12 @@ alias grep='grep --color=auto'
 # colored GCC warnings and errors
 export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'
 
+# Ensure ~/.local/bin is on PATH (pipx CLIs + personal scripts from bin/)
+case ":$PATH:" in
+	*":$HOME/.local/bin:"*) ;;
+	*) export PATH="$HOME/.local/bin:$PATH" ;;
+esac
+
 # Set history size to unlimited
 if [[ $EUID == 0 ]] ; then
 	export HISTSIZE=0