* Security: cap Slack media downloads and validate Slack file URLs
* Security: relax web media fetch cap for compression
* Fixes: sync pi-coding-agent options
* Fixes: align system prompt override type
* Slack: clarify fetchImpl assumptions
* fix: respect raw media fetch cap (#6639) (thanks @davidiach)
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Co-authored-by: Peter Steinberger <steipete@gmail.com>