fix(loop): C063 loop options audit — 6 discrepancy fixes

[pocky]

Summary

• Fixes 6 documentation-vs-implementation discrepancies found in a loop options audit: ~56 lowercase loop variable references (loop.item, loop.index) corrected to PascalCase (loop.Item, loop.Index) across 4 doc files
• Adds missing index1 and parent keys to makeLoopAccessor in template_resolver.go, enabling {{.loop.Index1}} and {{.loop.Parent.*}} to resolve correctly in templates
• Fixes silent bug where modulo (%) expressions in max_iterations were not routed to the arithmetic evaluator, causing them to be parsed as literal integers and fail
• Fixes nested loop Parent chain being silently dropped: ExecuteForEach now preserves the Parent field from buildContext output or falls back to buildLoopDataChain on the domain context

Changes

Documentation

• docs/reference/interpolation.md: Replaced all lowercase loop variable references with PascalCase; updated nested parent access examples
• docs/reference/loop.md: Replaced lowercase loop variable references with PascalCase across all examples and reference tables
• docs/user-guide/workflow-syntax.md: Updated for_each and while loop context tables (added Index1, Last, Item, Parent rows); corrected variable casing; replaced invalid arithmetic max_iterations example with single-variable form; improved while/break_when field descriptions
• docs/user-guide/examples.md: Corrected loop variable casing in for_each and nested loop examples
• CHANGELOG.md: Added C063 entry detailing all 6 findings and code changes
• CLAUDE.md: Added convention: apply code deletions before writing tests that validate the deletion effect

Implementation

• pkg/interpolation/template_resolver.go: Extracted loopToMap() helper; added index1 (Index+1) and parent (recursive map or nil) to loop accessor map
• internal/application/loop_executor.go: Added % to strings.ContainsAny operator detection in parseMaxIterationsValue; updated ExecuteForEach to preserve the Parent chain from buildContext output, with fallback to buildLoopDataChain from domain context

Tests

• pkg/interpolation/template_resolver_test.go: New file — tests for index1 (0-based, large), parent nil/value/recursive access, error on missing loop, and complex parent item serialization
• internal/application/loop_executor_refactor_test.go: Added modulo test case to table-driven suite; added 5 standalone tests covering modulo detection, error handling, and complex expressions
• internal/application/loop_foreach_test.go: Added 3 tests for buildContext equivalence verification, single-level parent nil assertion, and full iteration variable correctness after removing the redundant override
• internal/application/loop_iterations_test.go: Updated TestLoopExecutor_ResolveMaxIterations_ArithmeticModulo from negative test (expecting error) to positive test (expecting 2)
• internal/application/loop_executor_mocks_test.go: Added Parent field capture to stepExecutorRecorder

Test plan

• Run unit tests: go test ./pkg/interpolation/... ./internal/application/...
• Verify {{.loop.Index1}} and {{.loop.Parent.Item}} resolve correctly in a real nested for_each workflow
• Confirm max_iterations: "{{inputs.a % inputs.b}}" evaluates correctly (e.g., 7 % 3 → 1 iteration)
• Run full test suite: make test

Closes #264

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