fix: EWT/LWT loop flow anomaly fires on large delta, not small

[tim-ireland]

Summary

The previous rule warned when EWT/LWT delta was < 2°F, citing "loop flow restriction." This is physically backwards:

Q = flow_gpm × 500 × ΔT

A large ΔT at a given load means low flow — the pump isn't moving enough water. A small ΔT just means low compressor load or high flow rate, both normal.

Real example that triggered the false positive: 7-Series EWT 43.3°F / LWT 41.4°F = 1.9°F delta, system lightly loaded.

Fix: threshold changed to > 10°F (normal operating range is 5–10°F). Two tests added — one verifying the false-positive case is now silent, one verifying the corrected alert fires.

Test plan

• just test — 218 tests pass
• just lint — clean
• 7-Series anomaly at 1.9°F delta no longer appears in Intel log

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.06%. Comparing base (e78dadf) to head (eddabf2).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/flux-api/src/routes/intel.rs	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
+ Coverage   48.95%   49.06%   +0.10%     
==========================================
  Files          69       69              
  Lines        5619     5631      +12     
==========================================
+ Hits         2751     2763      +12     
  Misses       2868     2868              

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