refactor: reorganize into monorepo with separate subprojects

Structure webber into three independent subprojects:
- webber-api/: FastAPI backend server with all agent code
- webber-cli/: Standalone CLI client (renamed from cli/ to webber_cli/)
- webber-sandbox/: Test project for functional testing

Key changes:
- Each subproject has its own .venv (Python 3.12+)
- Added sandbox.sh for managing test project templates
- Created sandbox-templates/ with calculator-cli and empty starter
- Updated CI/CD for prefixed tags (api/v*, cli/v*)
- Added comprehensive AGENTS.md with operational instructions
- Added gitignore filtering to glob and grep tools
- Created pyproject.toml for each subproject

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

webber-api/src/domains/agents/utilities/askuserquestion-prompt.md

@@ -0,0 +1,15 @@
+<!--
+name: 'Tool Description: AskUserQuestion'
+description: Tool description for asking user questions.
+ccVersion: 2.0.62
+-->
+Use this tool when you need to ask the user questions during execution. This allows you to:
+1. Gather user preferences or requirements
+2. Clarify ambiguous instructions
+3. Get decisions on implementation choices as you work
+4. Offer choices to the user about what direction to take.
+
+Usage notes:
+- Users will always be able to select "Other" to provide custom text input
+- Use multiSelect: true to allow multiple answers to be selected for a question
+- If you recommend a specific option, make that the first option in the list and add "(Recommended)" at the end of the label