chore: cleanup from rushed debugging session
- fix ExtractedDocument docstring: only content/tags are allocated,
other fields borrow from parsed JSON
- add takeContent() method for clean ownership transfer pattern
(per arraylist.md: toOwnedSlice vs deinit patterns)
- use takeContent() in fetchLeafletContent instead of fragile
partial deinit that manually freed only tags
- remove verbose ACK logging that printed for every message
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>