Feature: Add Run support to LocalStorage (SDK v0.2.0)

Added run creation and management methods to LocalStorage:

1. create_run() - Create new run under experiment
   - Generates snowflake ID for run
   - Creates run directory structure (logs/, metrics/, files/)
   - Stores run metadata (id, name, status, timestamps)
   - Returns response matching remote API format

2. update_run_status() - Update run status
   - Find run by snowflake ID
   - Update status and timestamps
   - Set finished_at when status is terminal

3. _find_run_dir_by_id() - Helper to locate runs by ID
   - Searches across all projects/experiments
   - Returns run directory path

4. _get_run_dir() - Get run directory path
   - Helper method for run path resolution

This implements local storage support for the v0.2.0 run-based
architecture, enabling experiments to have multiple runs.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: tomtao57