next-dev-loop: require agent-browser >= 0.31.1 (#95209)
## Summary
Bump the `agent-browser` floor in the `next-dev-loop` skill from `>=
0.31.0` to `>= 0.31.1`.
One-line change to the `requires` section; the listed capabilities
(React introspection, worktree-scoped `session id`, idempotent
`--restore`, launch-flag reconciliation) are unchanged.
## Verification
- `prettier --check skills/next-dev-loop/SKILL.md` → clean.
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