Stabilize self-improvement v1 flow

[eloylp]

Summary

• simplify catalog version tracking so agents follow current published catalog assets instead of exact prompt/skill/guardrail pins
• stabilize the self-improvement proposal flow around queued analysis, clarification retries, proposal bundles, atomic publish, link-existing, and terminal decisions
• polish the dashboard flow with proposal/history tabs, inspect/clarify modals, stable catalog labels, 24-hour timestamps, and aligned docs

Verification

• GOCACHE=/tmp/go-build-agents go test ./internal/selfimprovement ./internal/store ./internal/workflow ./internal/daemon/observe ./internal/mcp
• npm test -- src/app/improvements/page.test.tsx src/app/skills/page.test.tsx
• npm run build
• git diff --check