v0.1.21

Added

• okf visualize <bundle_dir> — generates a self-contained interactive HTML graph of any OKF bundle using D3.js force-directed layout. Color-coded by concept type, searchable, with relationship edges (calls, imports, related). No server or install required.

Changed

• README restructured: demo GIF at top, feature cards, installation earlier, moved CLI reference and Python API to docs/ subpages.
• Banner updated to docs/banner.png.
• New demo GIF with real okf output.

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