fix: address second round of review comments

1. Log warning on auto-install failure instead of silent catch
2. Fix README install command (--from → --dev)
3. Bash: fail fast if resolve_template/json_escape unavailable after git-common.sh fallback
4. PowerShell: fail fast if Resolve-Template unavailable after git-common.ps1 fallback
5. Fix PowerShell $env:FEATURE_DIR → $FEATURE_DIR in specify.md
6. Fix docstring to reflect already-installed return value

Co-authored-by: mnriem <15701806+mnriem@users.noreply.github.com>
Agent-Logs-Url: https://github.com/github/spec-kit/sessions/6bcb7cb8-c7da-49d6-8206-1187766f92e1

extensions/git/scripts/powershell/create-new-feature.ps1

@@ -179,6 +179,14 @@ if (-not $commonLoaded) {
     throw "Unable to locate common script file. Please ensure the Specify core scripts are installed."
 }
 
+# If only git-common.ps1 was loaded, verify that Resolve-Template is available.
+# Resolve-Template is provided by the core common.ps1; git-common.ps1 only
+# supplies Test-HasGit / Test-FeatureBranch.
+if (-not (Get-Command Resolve-Template -ErrorAction SilentlyContinue)) {
+    throw ("Resolve-Template not defined. The core common.ps1 is required but could not be located. " +
+           "Tried: $PSScriptRoot/common.ps1, .specify/scripts/powershell/common.ps1, scripts/powershell/common.ps1")
+}
+
 try {
     $repoRoot = git rev-parse --show-toplevel 2>$null
     if ($LASTEXITCODE -eq 0) {