fix(migration): run migration during install, not on first execution (v3.1.1)

Fixed:

- Migration now runs during installation across all methods (npm, bash, PowerShell)

- Guarantees ~/.ccs/shared/ populated immediately with ~/.claude/ content

- Users no longer need to run ccs command to trigger migration

Changed:

- Refactored SharedManager with _needsMigration() and _performMigration() methods

- _copyDirectory() returns {copied, skipped} stats and preserves existing files

- Shows detailed migration output: '[OK] Migrated 5 commands, 19 skills'

- Removed lazy migration from bin/ccs.js, lib/ccs, lib/ccs.ps1

Implementation:

- npm: Migration in scripts/postinstall.js

- bash: Migration in installers/install.sh (migrate_shared_data function)

- PowerShell: Migration in installers/install.ps1 (Invoke-SharedDataMigration)

- Fixed arithmetic expansion with set -e (changed ((var++)) to var=$((var + 1)))

Cross-platform parity maintained across all installation methods.

lib/ccs

@@ -2,7 +2,7 @@
 set -euo pipefail
 
 # Version (updated by scripts/bump-version.sh)
-CCS_VERSION="3.1.0"
+CCS_VERSION="3.1.1"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 readonly CONFIG_FILE="${CCS_CONFIG:-$HOME/.ccs/config.json}"
 readonly PROFILES_JSON="$HOME/.ccs/profiles.json"
@@ -1010,9 +1010,6 @@ auto_recover || {
   exit 1
 }
 
-# Run migration to shared structure (Phase 1: idempotent)
-migrate_to_shared_structure
-
 # Smart profile detection: if first arg starts with '-', it's a flag not a profile
 if [[ $# -eq 0 ]] || [[ "${1}" =~ ^- ]]; then
   # No args or first arg is a flag → use default profile

lib/ccs.ps1

@@ -12,7 +12,7 @@ param(
 $ErrorActionPreference = "Stop"
 
 # Version (updated by scripts/bump-version.sh)
-$CcsVersion = "3.1.0"
+$CcsVersion = "3.1.1"
 $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"
@@ -1000,9 +1000,6 @@ if (-not (Invoke-AutoRecovery)) {
     exit 1
 }
 
-# Run migration to shared structure (Phase 1: idempotent)
-Migrate-SharedStructure
-
 # Smart profile detection: if first arg starts with '-', it's a flag not a profile
 if ($RemainingArgs.Count -eq 0 -or $RemainingArgs[0] -match '^-') {
     # No args or first arg is a flag → use default profile