fix: add dict type check for settings merge, simplify PS1 to subprocess

- _merge_vscode_settings() skips merge with warning if parsed JSON
  is not a dict (array, null, etc.)
- PS1 update-context.ps1 uses & invocation instead of dot-sourcing
  since the shared script runs Main unconditionally

Author: mnriem

src/specify_cli/integrations/copilot/__init__.py

@@ -171,6 +171,13 @@ def _merge_vscode_settings(src: Path, dst: Path) -> None:
 
         new_settings = json.loads(src.read_text(encoding="utf-8"))
 
+        if not isinstance(existing, dict) or not isinstance(new_settings, dict):
+            import logging
+            logging.getLogger(__name__).warning(
+                "Skipping settings merge: %s or template is not a JSON object.", dst
+            )
+            return
+
         for key, value in new_settings.items():
             if key not in existing:
                 existing[key] = value

src/specify_cli/integrations/copilot/scripts/update-context.ps1

@@ -10,29 +10,13 @@
 # refactored to support SPECKIT_SOURCE_ONLY (guard the Main call) before
 # dot-sourcing will work.
 #
-# Prerequisites (Stage 7):
-# - update-agent-context.ps1 must guard its Main call behind
-#   if (-not $env:SPECKIT_SOURCE_ONLY) { Main }
-# - Functions must be importable without side effects
+# Until then, this delegates to the shared script as a subprocess.
 
 $ErrorActionPreference = 'Stop'
 
 $repoRoot = git rev-parse --show-toplevel 2>$null
 if (-not $repoRoot) { $repoRoot = $PWD.Path }
 
-# Source shared utilities
-. "$repoRoot/.specify/scripts/powershell/common.ps1"
-
-# Source update-agent-context functions
-# SPECKIT_SOURCE_ONLY prevents the shared script from running its own main.
-$env:SPECKIT_SOURCE_ONLY = '1'
-. "$repoRoot/.specify/scripts/powershell/update-agent-context.ps1"
-
-# Gather feature paths and parse plan data
-$paths = Get-FeaturePathsEnv
-$implPlan = $paths.IMPL_PLAN
-Parse-PlanData -PlanFile $implPlan
-
-# Create or update the copilot instructions file
-$copilotFile = Join-Path $repoRoot '.github/copilot-instructions.md'
-Update-AgentFile -TargetFile $copilotFile -AgentName 'GitHub Copilot'
+# Invoke shared update-agent-context script as a separate process.
+# Dot-sourcing is unsafe until that script guards its Main call.
+& "$repoRoot/.specify/scripts/powershell/update-agent-context.ps1" -AgentType copilot