feat(mcp): add project context caching via MCP tools

[bborn]

Summary

• Add auto-generated project context caching that executors can read/write via MCP
• Eliminates the need for Claude to explore the codebase on every task startup
• Future tasks instantly get cached context, significantly speeding up task execution

Changes

1. DB Migration (internal/db/sqlite.go)

• Added context column to projects table for auto-generated context storage

2. DB Methods (internal/db/tasks.go)

• Added GetProjectContext(projectName string) - retrieves cached context
• Added SetProjectContext(projectName string, context string) - saves context

3. MCP Tools (internal/mcp/server.go)

• Added workflow_get_project_context tool - returns cached context for current task's project
• Added workflow_set_project_context tool - saves context to the project

4. Task Prompt Update (internal/executor/executor.go)

• Updated buildPrompt() to instruct Claude to use context caching

Flow

1. Task starts → Claude calls workflow_get_project_context
2. If context exists → Claude uses it, skips exploration
3. If empty → Claude explores once, calls workflow_set_project_context
4. Future tasks get cached context instantly

Test plan

• Run new unit tests for DB methods (TestProjectContext)
• Run new unit tests for MCP tools (TestWorkflowGetProjectContext, TestWorkflowSetProjectContext)
• Run full test suite (go test ./...)
• Verify build succeeds (go build ./...)
• Manual test: Start a task in a project without context, verify exploration happens
• Manual test: Start another task in the same project, verify cached context is used

🤖 Generated with Claude Code