feat(qol): add useful __repr__ to WorkspaceRunContext

[sohamwaghe]

Added __repr__ method to WorkspaceRunContext to make the object less opaque when inspecting in a REPL or debugger.

Output now shows:
`<WorkspaceRunContext(run_dir='/absolute/path/to/project', profile='dev')>

Related Issues

• Closes feat(qol): add useful __repr__ to WorkspaceRunContext #3941

Additional Context

• Added __repr__ to dlt/_workspace/_workspace_context.py using the codebase's existing simple_repr helper
• Added test in tests/workspace/test_workspace_context.py covering default and non-default profiles
• Follows Python convention of using < > to indicate the object cannot be re-instantiated from its repr

[sohamwaghe]

The test_load_arrow_vary_schema[arrow-table] failure looks unrelated to this PR — it's a DuckDB decimal casting error when loading parquet (22.1405 overflows DECIMAL(5,4)), happening in test_arrow_sources.py. My changes only touch _workspace/_workspace_context.py and tests/workspace/test_workspace_context.py. The matrix summary failure is just a downstream effect of that. Happy to rerun if needed!