fix(itg): restore failed incremental hashes for BUG-029

[sbalabanov]

Summary

Intent:

• BUG-029 requires failed incremental hash traversals to leave retryable graph state.

Changes:

• Track active recursion separately from persisted hashes and stage results until traversal succeeds.
• Cover a failed dependency hash, cache-format round trip, and successful retry on the same graph.

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Test Plan

AI Verification

Validated at 976b5e3 on Aug 26 18:25 UTC · 2 files analyzed · 1s

Validator	Status	Issues
go-lint	not_applicable	0
go-coverage	not_applicable	0
ios-lint	not_applicable	0
uber-one	not_applicable	0
go-thrift-lint	not_applicable	0
android-lint	not_applicable	0
java-lint	not_applicable	0
java-coverage	not_applicable	0
go-proto-lint	not_applicable	0
android-coverage	not_applicable	0
ios-test	not_applicable	0
web	not_applicable	0
diff-template	not_applicable	0
ureview	completed	0
custom	not_applicable	0

0 issues detected

_{Skipped validators: claude · EngWiki}

Issues

T3-BUG-029

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