set-openspec-path

Update openspecPath in .claude/project-context.json so the SessionStart hook injects the chosen project's openspec docs folder. This replaces hand-editing the absolute path with a menu choice.

Steps:

1. Read .claude/project-context.json from the current project root.
   • If the file does not exist, tell the user to run setup-project-context first and stop.
   • If it cannot be parsed as JSON, show the parse error and stop.