refactor(webui): apply Fat Gantt Shapes design to pipeline, issue, and PR detail pages

[nextlevelshit]

Context

The runs list and run detail pages have been redesigned with the Fat Gantt Shapes design (#707, branch feat/703-webui-fat-gantt-v2, 26 commits). The following pages still use the old v1 design and need to be updated to match.

Pages to redesign (priority order)

Detail pages

1. Pipeline detail (/pipelines/{name}) — pipeline_detail.html

   • Replace old DAG SVG + table with Fat Gantt step shapes
   • Steps as clickable shapes showing persona, contract, artifacts, prompt
   • Recent runs as v2 card list (not table)
   • Quickstart dialog matches v2 design

2. PR detail (/prs/{number}) — pr_detail.html

   • Rich PR card: title, state, diff stats, checks, reviews
   • Related pipeline runs as v2 cards
   • Match IN/OUT card design from run detail

3. Issue detail (/issues/{number}) — issue_detail.html

   • Rich issue card: title, state, labels, description
   • Related pipeline runs
   • Match IN card design

Overview/list pages

4. Pipelines list (/pipelines) — pipelines.html
5. Issues list (/issues) — issues.html
6. PRs list (/prs) — prs.html
7. Contracts list (/contracts) — contracts.html
8. Personas list (/personas) — personas.html
9. Contract detail (/contracts/{name}) — contract_detail.html
10. Persona detail (/personas/{name}) — persona_detail.html

Design principles (Frictionless AI Factory)

• No raw URLs — parse forge URLs into rich context
• No raw JSON — smart-render with severity cards
• No placeholder text — real, meaningful data everywhere
• No raw model IDs — friendly names (Haiku, Sonnet)
• Every field answers a human question
• First-shot quality
• No emojis — SVG icons or HTML entities only

Completed

• Runs list (/runs)
• Run detail (/runs/{id})

Related: #707, #708