v0.4.0 - render progress and cancel

Install: download simutrans_blender_kit.zip below, then in Blender go to Edit → Preferences → Add-ons → Install…, pick the zip, and enable "Simutrans Blender Kit".

Added

• Render Sheet shows progress and can be cancelled. A vehicle render fires the renderer eight times with the UI frozen and no way out. It now renders one heading per tick with a progress bar and a status-bar readout (heading N/8), and Esc stops it. Because the render call is itself blocking, the gain is an update-and-cancel point between headings — which is where the seconds actually go. A cancelled render is left on disk but not recorded, so Write .dat still builds only from the last complete render, never half a sheet.

Changed

• CI runs the core suite on every push (GitHub Actions, Python 3.10–3.12): the ~970 Blender-free checks — projection, colours, the .dat linter, schema drift.
• doc_url and the README now point at the GitHub repository and its releases.

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Everything from v0.3.0 is included. The progress/cancel path was verified by hand in Blender 5.1 (headless has no event loop, so the modal operator cannot be covered by the automated suite); execute(), the shared reporter, and the new strings are covered by the green core and panel suites.