chore(ci): bump umm-actually to v0.4.8

[aliasunder]

Bumps the umm-actually review action pin from v0.4.7 to v0.4.8.

v0.4.8 changes:

• Priority docs read first. Up to 10% of the context budget now goes to priority docs before changed files are read, so a large diff can no longer crowd them out.
• Findings name their model. When phases route to different models, each finding's byline names the model that produced it.

No new inputs in this release, so the template changes only the pin.

🤖 Generated with Claude Code

[umm-actually]

umm-actually re-reviewed at f6ba1eb

No new findings (0 tracked finding(s) across all runs).

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umm-actually · deepseek/deepseek-v4-flash-0731