feat: add Explore agent with PydanticAI tool calling

Implements the first Claude-like agent for codebase exploration:

Core Features:
- Explore agent with glob, grep, read, and bash tools
- Native PydanticAI tool calling with Ollama/Mistral Nemo
- Sanitized Ollama provider (fixes content:null issue)
- REST API endpoints for agent execution

Tool Infrastructure:
- BaseTool abstract class with ToolResult dataclass
- ReadFileTool, GlobFilesTool, GrepContentTool, BashReadOnlyTool
- Path validation and sandboxing support

CLI Client (separate package for future extraction):
- webber-cli command with chat, explore, status commands
- Communicates with Webber API backend
- Rich console output with theming

Configuration:
- Dev server on port 8095 (production uses 8086)
- Mistral Nemo optimizations (temp 0.3, tool_choice required)

Tests: 24 tests covering tools and API endpoints

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

pyproject.toml

@@ -15,13 +15,17 @@ classifiers = [
     "Topic :: Software Development :: Code Generators",
 ]
 
+[project.scripts]
+webber = "src.cli.main:app"
+webber-cli = "cli.main:app"
+
 [build-system]
 requires = ["setuptools>=75.0", "wheel"]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools.packages.find]
 where = ["."]
-include = ["src*"]
+include = ["src*", "cli*"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]