chore: clean outdated artifacts + improve build script

Cleanup:
- Remove SAFETY_INSTRUCTIONS_AUDIT.md (completed audit)
- Remove docs/plans/provider-agnostic-response-integrity.md (completed)
- Remove docs/research/provider-agnostic-response-integrity.md (completed)
- Remove docs/audit-custom-task-title.md (completed)
- Remove docs/architecture-research-custom-task-title.md (completed)
- Remove docs/architecture-validation-custom-task-title.md (completed)
- Remove progress.txt (old progress tracking)

Build script improvements:
- Add prerequisites check (node, pnpm, git)
- Add -OnlyVsix quick mode flag
- Add -SkipInstall flag
- Add SHA-256 hash output for artifact
- Add full artifact details in summary

Author: CodeKing

SAFETY_INSTRUCTIONS_AUDIT.md

@@ -1,31 +1,44 @@
 <#
 .SYNOPSIS
-    Full build pipeline: type-check, test, and package VSIX.
+    Full build pipeline: install, type-check, test, and package VSIX.
 
 .DESCRIPTION
     Runs the complete build process for Zoo-Code:
-    1. TypeScript type-check across all packages
-    2. Unit tests via turbo
-    3. VSIX packaging
+    1. Check prerequisites (node, pnpm, git)
+    2. Install dependencies (pnpm install)
+    3. TypeScript type-check
+    4. Unit tests
+    5. VSIX packaging
+    6. Artifact verification (path, size, SHA-256)
 
     Stops on first failure with a clear error message.
 
 .EXAMPLE
-    .\build.ps1
-    .\build.ps1 -SkipTests
-    .\build.ps1 -SkipTypes
+    .\build.ps1                          # Full pipeline
+    .\build.ps1 -SkipTests               # Skip tests
+    .\build.ps1 -OnlyVsix                # Just build VSIX (skip types + tests)
+    .\build.ps1 -SkipInstall             # Skip pnpm install (already installed)
 #>
 
 param(
     [switch]$SkipTypes,
     [switch]$SkipTests,
     [switch]$SkipVsix,
-    [int]$TimeoutSec = 300
+    [switch]$SkipInstall,
+    [switch]$OnlyVsix,
+    [int]$TimeoutSec = 600
 )
 
 $ErrorActionPreference = "Stop"
 $scriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
 
+# OnlyVsix shorthand
+if ($OnlyVsix) {
+    $SkipTypes = $true
+    $SkipTests = $true
+    $SkipInstall = $true
+}
+
 function Write-Step($step, $msg) {
     Write-Host "`n========================================" -ForegroundColor Cyan
     Write-Host "  [$step] $msg" -ForegroundColor Cyan
@@ -68,28 +81,59 @@ Push-Location $scriptDir
 try {
     $global:stepCounter = 1
 
-    # 1. Type-check
+    # 0. Prerequisites
+    Invoke-BuildStep "Check Prerequisites" {
+        $nodeVer = & node --version 2>&1
+        if ($LASTEXITCODE -ne 0) { throw "Node.js not found. Install Node.js 20.x" }
+        Write-Host "  Node.js: $nodeVer" -ForegroundColor DarkGray
+
+        $pnpmVer = & pnpm --version 2>&1
+        if ($LASTEXITCODE -ne 0) {
+            Write-Host "  pnpm not found, enabling via corepack..." -ForegroundColor DarkYellow
+            & corepack enable 2>&1
+            $pnpmVer = & pnpm --version 2>&1
+            if ($LASTEXITCODE -ne 0) { throw "pnpm not available. Run: corepack enable" }
+        }
+        Write-Host "  pnpm: $pnpmVer" -ForegroundColor DarkGray
+
+        $gitVer = & git --version 2>&1
+        if ($LASTEXITCODE -ne 0) { throw "Git not found" }
+        Write-Host "  Git: $gitVer" -ForegroundColor DarkGray
+    }
+
+    # 1. Install dependencies
+    if (-not $SkipInstall) {
+        Invoke-BuildStep "Install Dependencies" {
+            & pnpm install --frozen-lockfile
+        }
+    } else {
+        Write-Host "[SKIP] Install dependencies" -ForegroundColor DarkYellow
+    }
+
+    # 2. Type-check
     if (-not $SkipTypes) {
         Invoke-BuildStep "TypeScript Type-Check" {
-            pnpm check-types
+            Push-Location src
+            try { & pnpm run check-types }
+            finally { Pop-Location }
         }
     } else {
         Write-Host "[SKIP] TypeScript type-check" -ForegroundColor DarkYellow
     }
 
-    # 2. Tests
+    # 3. Tests
     if (-not $SkipTests) {
         Invoke-BuildStep "Unit Tests" {
-            pnpm test
+            & pnpm test
         }
     } else {
         Write-Host "[SKIP] Unit tests" -ForegroundColor DarkYellow
     }
 
-    # 3. VSIX
+    # 4. VSIX
     if (-not $SkipVsix) {
         Invoke-BuildStep "VSIX Packaging" {
-            pnpm vsix
+            & pnpm vsix
         }
     } else {
         Write-Host "[SKIP] VSIX packaging" -ForegroundColor DarkYellow
@@ -104,10 +148,16 @@ try {
         $vsix = Get-ChildItem -Path "bin\*.vsix" -ErrorAction SilentlyContinue | Sort-Object LastWriteTime -Descending | Select-Object -First 1
         if ($vsix) {
             $sizeMB = [math]::Round($vsix.Length / 1MB, 2)
-            Write-Host "`nOutput: bin\$($vsix.Name) ($sizeMB MB)" -ForegroundColor Green
+            $hash = (Get-FileHash -Path $vsix.FullName -Algorithm SHA256).Hash
+            Write-Host "`nArtifact Details:" -ForegroundColor Green
+            Write-Host "  Path:   $($vsix.FullName)" -ForegroundColor White
+            Write-Host "  Size:   $($vsix.Length) bytes ($sizeMB MB)" -ForegroundColor White
+            Write-Host "  SHA256: $hash" -ForegroundColor White
+        } else {
+            Write-Host "`n[WARN] No VSIX found in bin/" -ForegroundColor DarkYellow
         }
     }
 }
 finally {
     Pop-Location
-}
+}