fix: assist_pattern_key reads username from credential.username for exploit payloads

[l50]

Key Changes:

• Enhanced username and domain extraction in assist_pattern_key to handle nested credential fields
• Fixed exploit deduplication logic to prevent repeated retries due to missed credential fields
• Added comprehensive tests for username/domain extraction priority and fallback behavior

Added:

• Test cases covering various payload shapes, including nested credential objects, username/domain precedence, pass-the-hash scenarios, and cross-forest exploits

Changed:

• Username extraction now prioritizes top-level "username", then falls back to "credential.username", and finally "hash_username"
• Domain extraction now prefers top-level "domain", with fallback to "credential.domain" to avoid key collisions across forests
• Updated documentation and inline comments to clarify lookup priorities and rationale for changes

Removed:

• Implicit assumption that username/domain fields are always top-level, reducing risk of exploit deduplication failures

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.06%. Comparing base (72fa578) to head (b6ddb39).

Additional details and impacted files

@@                   Coverage Diff                    @@
##           feat/more-attack-cov     #312      +/-   ##
========================================================
+ Coverage                 76.05%   76.06%   +0.01%     
========================================================
  Files                       439      439              
  Lines                    118188   118258      +70     
========================================================
+ Hits                      89884    89954      +70     
  Misses                    28304    28304              

Files with missing lines	Coverage Δ
ares-cli/src/orchestrator/dispatcher/submission.rs	19.47% <100.00%> (+11.16%)	⬆️

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