feat(completion): improve fish shell completion with category prefixes (#14)

* feat(completion): improve fish shell completion with category prefixes

- Remove problematic inline set_color commands that prevented descriptions from displaying
- Add [cmd], [model], and [account] prefixes to visually group completions
- Update file header to document categorization features

This brings fish completion quality closer to zsh by making categories
clear and ensuring descriptions actually display to users.

Fixes issue where fish completions showed no descriptions.

* chore: bump version to 4.3.1

lib/ccs

@@ -2,7 +2,7 @@
 set -euo pipefail
 
 # Version (updated by scripts/bump-version.sh)
-CCS_VERSION="4.3.0"
+CCS_VERSION="4.3.1"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 readonly CONFIG_FILE="${CCS_CONFIG:-$HOME/.ccs/config.json}"
 readonly PROFILES_JSON="$HOME/.ccs/profiles.json"

lib/ccs.ps1

@@ -12,7 +12,7 @@ param(
 $ErrorActionPreference = "Stop"
 
 # Version (updated by scripts/bump-version.sh)
-$CcsVersion = "4.3.0"
+$CcsVersion = "4.3.1"
 $ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
 $ConfigFile = if ($env:CCS_CONFIG) { $env:CCS_CONFIG } else { "$env:USERPROFILE\.ccs\config.json" }
 $ProfilesJson = "$env:USERPROFILE\.ccs\profiles.json"