Agent timelines can handle long conversations better

The agent transcript view was rebuilt around virtualized rows, height indexes, visible range policy, and row stores. Long-running agent sessions should scroll more smoothly without forcing every transcript row to stay mounted.

• Added KajiAgentTimelineRow, row store, height estimator, height index, and visible range policy
• Added KajiAgentVirtualTimelineView and row height reading
• Added timeline flattener and row spacing policy
• Improved scroll lock behavior for active agent output
• Added extensive tests for timeline virtualization and scrolling

Transcripts render richer markdown and collapsible tool output

Agent output now has a richer markdown parsing and rendering pipeline, including code blocks, long text handling, streaming markdown, thinking rows, and accordion-style disclosure rows for dense output.

• Added KajiAgentMarkdownModels and KajiAgentMarkdownParser
• Added KajiAccordionItem, KajiAgentCodeBlockView, KajiAgentLongTextView, and streaming markdown views
• Added inline semantic parsing for transcript text
• Added tool call rows, tool output views, and grouped tool headers
• Added markdown parser and inline parser tests

Kaji Agent custom providers arrived

Custom provider configuration was added to both the native app and the agent runtime, including Azure OpenAI deployment discovery and normalized provider config handling.

• Added KajiAgentCustomProvider models, auto-match behavior, enums, and model configuration
• Added custom provider settings editor, model editor, rows, and section UI
• Added runtime custom provider config normalization and model registry support
• Added Azure OpenAI deployment discovery tests
• Bumped Kaji to 0.2.8