fix(repomanager): sanitize reused workers for BUG-003

[sbalabanov]

Summary

BUG-003 prevents changes left by one request from affecting the next request that reuses the same repository worker.

• Before the next git checkout and workspace changes, reset tracked files and remove untracked, ignored, and submodule changes.
• If the worker cannot be cleaned, delete and clone it again instead of reusing it.

Test Plan

• Verified that a failed request leaving staged, tracked, untracked, and ignored changes is followed by a clean checkout.
• Verified that cleanup failure recreates the worker.

AI Verification

Validated at 31d76b4 on Aug 26 18:11 UTC · 6 files analyzed · 1s

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

0 issues detected

_{Skipped validators: claude · EngWiki}

Issues

T3-BUG-003

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[sbalabanov]

update PR description to use concrete wording, like "git checkout" instead of "materialization". Simplify.

[sbalabanov]

Addressed review 5036024575 at HEAD 31d76b4006bea0a98fbd0d26714d2162c864b966. Simplified the BUG-003 description to explain the concrete git checkout, cleanup, and worker recreation behavior. This was metadata-only; no code or commit changes were made.

[addressed by agent]