Use effective identity for DryRunEvaluator node_key

[ptomecek]

Summary

DryRunEvaluator reports a node_key for each planned node. That key was derived from the raw structural cache_key(...) (effective=False), so it ignored the opt-in _CallableModel._evaluation_identity_payload() effective-identity hook.

Meanwhile, the in-process MemoryCacheEvaluator.key and the dependency-graph dedup (_build_dependency_graph) already key on cache_key(..., effective=True). As a result, a model that opts into a collision-safe effective identity was reported under the structural key in dry-run plans — inconsistent with how the same node is actually cached and deduplicated. For models whose distinct structural keys collapse, this could silently merge or mislabel distinct nodes in the plan/report.

Fix

Pass effective=True when building the dry-run node_key.

• For models that opt out (the base hook returns None), this is a byte-for-byte no-op and preserves the existing structural key.
• For opt-in models, the plan now reflects their effective identity, consistent with memory/graph dedup.

Test

Adds test_node_key_uses_effective_identity: a generated @Flow.model that ignores an unused ambient context field. The emitted node_key must equal cache_key(..., effective=True) and must merge two contexts that differ only in an ignored field — even though their structural keys differ.

Validation

ccflow/tests/evaluators/ and ccflow/tests/test_effective_key_characterization.py pass (75 tests), including all pre-existing dry-run tests.

[github-actions]

Test Results

    1 files  ±0      1 suites  ±0   3m 17s ⏱️ +17s
1 329 tests +1  1 327 ✅ +1  2 💤 ±0  0 ❌ ±0 
1 335 runs  +1  1 333 ✅ +1  2 💤 ±0  0 ❌ ±0 

Results for commit b80b76a. ± Comparison against base commit 6a788a6.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

❌ Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 93.48%. Comparing base (6a788a6) to head (b80b76a).

Files with missing lines	Patch %	Lines
ccflow/tests/evaluators/test_reporting.py	95.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #262   +/-   ##
=======================================
  Coverage   93.48%   93.48%           
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  Files         176      176           
  Lines       20327    20347   +20     
  Branches     1350     1350           
=======================================
+ Hits        19002    19021   +19     
- Misses       1052     1053    +1     
  Partials      273      273           

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