feat(web): ui kit and task conversation refresh

[naashw]

• feat(web): add the UI kit foundations, Cascadia Mono and the theme picker
• refactor(web): map the legacy colour, font and size tokens onto the kit tokens
• feat(web): give every task status a semantic tone and a data-tone kit rule
• fix(cli): mirror the palette bootstrap into the dev index template
• feat(web): port the task composer and repo settings to the kit
• feat(web): port the pilot deck to the kit
• feat(web): port the workspace shell, rails and repository views to the kit
• feat(web): port the review surfaces to the kit
• feat(web): split the task conversation and port it with the events to the kit
• feat(web): port the review prologue to the kit
• feat(web): port the forge board and merge request views to the kit
• feat(web): split the diff view and port it with the changes panel to the kit
• refactor(web): retire the legacy stylesheet, fonts and Tailwind bridge behind the kit guards
• style(web): flatten the pilot deck and composer to one frame per component
• style(web): flatten the rails, repository, forge and MR surfaces
• style(web): flatten the conversation and its events to left rails
• style(web): flatten the review, diff and changes surfaces
• feat(web): one-column pilot shell with the conversations list on the left
• style(web): let the pilot conversation take the full remaining width
• style(web): plain tree lines in the conversations rail
• style(web): a conversation line is its title and time between two inset hairlines
• feat(web): classic shell by default and a wider left list
• feat(web): one flat list of conversations in the rail
• refactor(web): drop the pilot shell, polish the rails and move the theme picker into the rail
• feat(web): derive a short conversation label from the agent-named branch
• feat(web): one header band, short conversation labels and an icons-only rail
• feat(web): inline timestamps, danger zone, left-aligned user messages and a folded setup line
• fix(web): one search line for the rail lists, blue in-flight turns and a 30ch rail
• feat(web): near-monochrome conversation with one filled block and no rails
• feat(web): render markdown in live bubbles, with blockquotes, tables and rules