Improve nearBalancedPool check

[sparrowDom]

Summary

Relax StableSwapAMMStrategy.nearBalancedPool so the peg check works on pools that are 100–1000× smaller than what the previous probe size required. The check previously failed on the live Hydrex superOETHb/WETH pool (~0.0009 ETH/side) even when the pool was perfectly balanced, because the hard-coded 1 ETH probe was 1000× the pool's reserves — getAmountOut was returning ~the entire pool, not a real marginal-price quote.

Effective floor

Old: pool needed ~50 WETH/side for deposit() to clear the peg check. New: pool needs ~0.05 WETH/side (1000× smaller). Below ~1000 wei reserves the modifier reverts with Pool too small (intentional — an empty pool can't be safely deposited into).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.72%. Comparing base (cd7218c) to head (2576da6).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2898      +/-   ##
==========================================
+ Coverage   50.68%   50.72%   +0.04%     
==========================================
  Files         110      110              
  Lines        4873     4877       +4     
  Branches     1353     1354       +1     
==========================================
+ Hits         2470     2474       +4     
  Misses       2399     2399              
  Partials        4        4              

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