feat(search): Add search index cache infrastructure

Add init_search_cache() and build_search_cache() functions that
create and validate a JSON-based binary index stored at
$scoopdir/search-cache.json.

The cache maps every app name to its file path and bucket, and
every binary name (without extension) to the app(s) that expose it.
Staleness is detected via timestamp (<24h) and file-count cross-check
using the same recursive Get-ChildItem enumeration as the regex path.

Author: B67687

libexec/scoop-search.ps1

@@ -14,6 +14,83 @@ param($query)
 
 $list = [System.Collections.Generic.List[PSCustomObject]]::new()
 
+# === Search index cache (JSON-based, faster than SQLite) ===
+$searchCachePath = Join-Path $scoopdir 'search-cache.json'
+$searchIndexApps = $null
+$searchIndexBins = $null
+
+function init_search_cache {
+    if (-not (Test-Path $searchCachePath)) { return $false }
+    try {
+        $cache = Get-Content $searchCachePath -Raw | ConvertFrom-Json -ErrorAction Stop
+        $cacheAge = (Get-Date) - [datetime]::Parse($cache.timestamp)
+        if ($cacheAge.TotalHours -ge 24) { return $false }
+        # Cross-check file count for staleness
+        $currentCount = 0
+        Get-LocalBucket | ForEach-Object {
+            $dir = Find-BucketDirectory $_
+            $currentCount += (Get-ChildItem $dir -Filter '*.json' -Recurse -ErrorAction SilentlyContinue).Count
+        }
+        if ($cache.fileCount -ne $currentCount) { return $false }
+        $script:searchIndexApps = @{}
+        foreach ($prop in $cache.apps.PSObject.Properties) {
+            $script:searchIndexApps[$prop.Name] = @{ path = $prop.Value.path; bucket = $prop.Value.bucket }
+        }
+        $script:searchIndexBins = @{}
+        foreach ($prop in $cache.bins.PSObject.Properties) {
+            $script:searchIndexBins[$prop.Name] = @($prop.Value)
+        }
+        return $true
+    } catch { return $false }
+}
+
+function build_search_cache {
+    $allPathsByBucket = @{}
+    Get-LocalBucket | ForEach-Object {
+        $dir = Find-BucketDirectory $_
+        $paths = @(Get-ChildItem $dir -Filter '*.json' -Recurse -ErrorAction SilentlyContinue | ForEach-Object { $_.FullName })
+        if ($paths.Count -gt 0) { $allPathsByBucket[$_] = $paths }
+    }
+    $totalCount = ($allPathsByBucket.Values | ForEach-Object { $_.Count } | Measure-Object -Sum).Sum
+    $newApps = @{}
+    $newBins = @{}
+
+    foreach ($bucket in $allPathsByBucket.Keys) {
+        foreach ($filePath in $allPathsByBucket[$bucket]) {
+            $appName = [System.IO.Path]::GetFileNameWithoutExtension($filePath)
+            $newApps[$appName] = @{ path = $filePath; bucket = $bucket }
+            try {
+                $manifest = Get-Content -Path $filePath -Raw | ConvertFrom-Json -ErrorAction Stop
+                if (-not $manifest.bin) { continue }
+                foreach ($binEntry in $manifest.bin) {
+                    $exe = $null; $alias = $null
+                    if ($binEntry -is [System.Object[]]) {
+                        $exe = $binEntry[0]
+                        $alias = if ($binEntry.Count -gt 1) { $binEntry[1] } else { $null }
+                    } else { $exe = $binEntry }
+                    $exeName = [System.IO.Path]::GetFileNameWithoutExtension([string]$exe).ToLower()
+                    if ($exeName) {
+                        if (-not $newBins.ContainsKey($exeName)) { $newBins[$exeName] = @() }
+                        if ($appName -notin $newBins[$exeName]) { $newBins[$exeName] += $appName }
+                    }
+                    if ($alias) {
+                        $aliasName = $alias.ToLower()
+                        if ($aliasName) {
+                            if (-not $newBins.ContainsKey($aliasName)) { $newBins[$aliasName] = @() }
+                            if ($appName -notin $newBins[$aliasName]) { $newBins[$aliasName] += $appName }
+                        }
+                    }
+                }
+            } catch { }
+        }
+    }
+    $cacheData = [PSCustomObject]@{ timestamp = (Get-Date).ToString('o'); fileCount = $totalCount; apps = [PSCustomObject]$newApps; bins = [PSCustomObject]$newBins }
+    $cacheData | ConvertTo-Json -Compress -Depth 4 | Set-Content $searchCachePath -Encoding UTF8
+    $script:searchIndexApps = $newApps
+    $script:searchIndexBins = $newBins
+    return $true
+}
+
 function bin_match($manifest, $query) {
     if (!$manifest.bin) { return $false }
     $bins = foreach ($bin in $manifest.bin) {