The native vision_analyze fast path (and the browser screenshot twins) downscaled every
embed to a fixed _EMBED_TARGET_BYTES = 256 KB. That is fine for photos but turns a
1080x2340 phone screenshot of a table into 540x1170, which the model then reads as
"unreadable" and re-requests (#112095).
The budget is now `vision.embed_target_bytes` in config.yaml (default unchanged: 256 KB,
clamped to 64 KiB..4 MiB so one setting cannot make every later request a multi-megabyte
resend), resolved in the new topical sibling tools/vision_tools_history_budget.py and read
by vision_analyze, browser_vision and browser_exec screenshots alike.
Ported from #112947 by @MohamadKanso (resolver + clamp), relocated out of the facade.
