docs(knowledge): add theme-color checklist and markdown rendering architecture

New knowledge entries documenting the steps for adding theme colors and
the TUI markdown rendering pipeline.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: d4ncer

.ralph/knowledge/theme-color-addition-checklist.md

@@ -0,0 +1,20 @@
+---
+title: "Theme Color Addition Checklist"
+tags: [ui, theme, color, input]
+created_at: "2026-02-26T04:17:39.349012+00:00"
+---
+
+When adding a new color to the TUI theme system, all these locations must be updated:
+
+1. `Theme` struct field in `src/ui/theme.rs`
+2. `Theme::dark()` constructor
+3. `Theme::light()` constructor
+4. `ColorOverrides` struct (with `Option<String>` field)
+5. `ColorOverrides::validate()` field list
+6. `ColorOverrides::apply_to()` set call
+7. Style accessor function (e.g. `pub fn input_text() -> Style`)
+8. `color_overrides_all_fields` test
+
+Use `Color::Reset` when you want the terminal's native fg/bg to show through — this is the safest default for text that must be readable on any terminal background.
+
+See also: [[Ratatui UI Runtime]], [[TUI Input Model (v0.8.1+)]]

.ralph/knowledge/tui-markdown-rendering-architecture.md

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+---
+title: "TUI Markdown Rendering Architecture"
+tags: [ui, theme, markdown, tui, view]
+created_at: "2026-02-26T04:49:57.071673+00:00"
+---
+
+Agent stream markdown rendering in the TUI uses ratatui native `Span`/`Line` styling (not ANSI escapes). The rendering pipeline:
+
+1. `src/ui/state.rs` — `AgentText` events: trims leading whitespace on first chunk, collapses 3+ consecutive newlines into 2
+2. `src/ui/view.rs` — `render_agent_markdown()` parses `state.agent_text` into `Vec<Line<'static>>` with styled spans
+3. Supported elements: fenced code blocks (code_block style), headings (heading style, bold), blockquotes (italic, `│` prefix), list bullets (colored bullet/number), horizontal rules (40-char `─` line), inline code/bold/italic/links
+4. `parse_inline_markdown()` handles inline elements returning `Vec<Span<'static>>`
+
+Tool activity uses `ToolLine { name, summary }` struct. Detail lines have empty `name`. Rendered as: tool_name style + accent arrow + subdued summary.
+
+Theme tokens added in v0.8.1+: `heading_fg`, `code_span_fg`, `code_block_fg`, `link_fg`, `blockquote_fg`, `list_bullet_fg`, `hr_fg`, `accent_fg`, `tool_name_fg`. All support `[ui.colors]` overrides.
+
+See also: [[Themeable TUI Colour Scheme]], [[Ratatui UI Runtime]], [[UI Event Routing and Plain Fallback]]