feat(02-03): add prompt template files

- prompts/__init__.py: Package marker
- context_recovery.md: Session context recovery prompt
- command_mapping.md: User input to GSD command mapping
- error_recovery.md: User-friendly error message generation

All templates use {{variable}} syntax for substitution.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gsd-openclaw/src/gsd_openclaw/prompts/command_mapping.md

@@ -0,0 +1,21 @@
+# Command Mapping
+
+Map the following user input to a GSD slash command.
+
+## User Input
+{{user_input}}
+
+## Available Commands
+- /gsd:new-project <name> - Create a new project
+- /gsd:use <project> - Switch to a project
+- /gsd:status - Show current status
+- /gsd:plan - Run planning phase
+- /gsd:ship - Ship current phase
+- /gsd:help - Show help
+
+## Current Context
+- Project: {{current_project}}
+- Phase: {{current_phase}}
+
+## Instructions
+Determine the most appropriate command based on the user input and context.