Unreleased changes

• Add OpenAI Fast mode (#1657). Allow it per model in Settings → Models for a ChatGPT subscription or an OpenAI Responses connection, then type /fast to turn it on for the current conversation. Requests ask for the priority service tier, which replies faster and spends plan limits faster or bills more per token; the Composer model chip shows a Fast mark while it is on.
• Fixed an older regenerated prompt appearing after the latest reply when its branch archive completed outside the loaded history window (#1870). Pager acknowledgements now update existing rows without appending historical roots.
• Generate inline visualizations faster. The visualization shell now preloads the bundled D3 and a viz chart helper layer (container sizing, resize and theme redraw, axes, tick overlap, legends, and a declarative viz.render for bar, line, area, point, heatmap, and donut charts), so model-written fragments are shorter. The visualize skill asks for a single write followed by the reply instead of reading the file back. Fragments written under the earlier skill keep rendering. When a fragment's script fails, the card now says so and shows the error instead of staying blank, and the model's write result flags syntax errors and missing chart containers so it can fix them with one edit.