feat(webapp): TRI-12763 agent UI polish

- header aligned with the title bar; custom +/x icons; history as a title
  dropdown popover with shorthand ages and delete confirm
- composer: tighter corners, icon-only send/stop, context path above the field
- chat bubbles: assistant text is plain prose, user bubbles grey
- agent-identity.ts single source for name/icon (TODO: character icon from design)
- Help & Feedback: 'Ask Agent' (cmd+J) via open-request bridge; Kapa AI fully removed
- free plan: 20-message cap with upgrade gate and countdown notice
- storybook canvas matches the panel background; chart min-height and padding

Author: kathiekiwi

.server-changes/ask-agent-replaces-ask-ai.md

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+---
+area: webapp
+type: improvement
+---
+
+Ask AI has been replaced by the dashboard agent everywhere it used to appear — the Help & Feedback menu, the deployment setup panels, and the link the CLI prints when a task errors. Chat answers now read as plain text instead of stacked cards, and on the Free plan you get 20 messages before an upgrade is needed (your past chats stay readable).