Dedicated Skills pages, smoother chat, and richer markdown editing

This update improves the day-to-day editing and chat workflow inside SupaPM. Skills now behave more like first-class documents, with list and detail pages instead of modal editing, and the chat composer sits inside the chat surface where it belongs.

What's new

• Dedicated Skills pages: Skills now use index and detail routes, making them easier to scan, open, create, and edit.
• Markdown-style Skills editing: Skill instructions use the same richer markdown rendering approach as project and org knowledge documents.
• More cohesive side panel chat: The composer is part of the chat card, keeping the conversation and input together.
• Smoother streaming: Streaming follows the bottom of the conversation only when you are already there, so reading older messages is less frustrating.
• Less abrupt scrolling: Removed side panel scroll snapping for a calmer stacked layout.
• Markdown editor improvements: Centralized markdown styles, refined table/code/blockquote rendering, and added Notion-style date mentions such as @today and @next monday.

This release is mostly about reducing friction for people who use SupaPM every day.