Retry once when the batch signer returns a partial map

[stevevanhooser]

Summary

• Adds a bounded one-shot retry to ndi.cloud.download.internal.batchSignedUrlLookup for the case where the presign endpoint answers with a populated map that does not name a requested uid (a "partial map"). On the miss, the helper drops the entry, pauses briefly, and re-fetches once. If the second answer covers the uid, every subsequent uid in the same scope resolves from the refreshed cache; if not, the caller falls back per uid as before and the scope's warning fires. Bounded to one retry per scope, so a genuine data-drift miss still costs one extra signer call for the whole scope, not one per uid.
• New STATS.partialMapRetries counter so tests can distinguish the retry path from a plain data-drift miss.
• Refactor: the fetch/nargout/try dance moves into a nested localFetchScope so the retry can call it a second time without duplicating it. Adds an injectable sleepFcn (default @pause) and a partialMapRetrySeconds option so tests exercising the retry do not pay real wall-clock latency.
• Relaxes FileSeriesRoundTripTest.signerCalls to 1 + batchStats.partialMapRetries with partialMapRetries <= 1, keeping the "one batch call per series' worth of members" contract while allowing the retry. uidMisses == 0 stays firm.

Motivation

Waltham-Data-Science/NDI-python#309 saw the second case on TEST_USER_1/prod after Waltham-Data-Science/NDI-python#308 first let a series manifest reach the server: the batch answered signer_calls=1 with a 2-entry map for a 4-member series. Re-running the same job 37 minutes later returned the full 4-entry map — so the batch endpoint does eventually catch up, just not by the time waitForAllBulkUploads reports done. The MATLAB helper has the same shape and the same risk. This PR is the MATLAB counterpart of Waltham-Data-Science/NDI-python#310, which merged the same fix on the Python side.

Closes #991.

Test plan

• runtests('ndi.unittest.BatchSignedUrlLookupTest') — the four new testPartialMapRetry* tests cover retry-succeeds, retry-pauses, retry-once-per-scope, and retry-raises-and-falls-back; existing miss-path tests updated for the added signer call.
• runtests('ndi.unittest.cloud.FileSeriesRoundTripTest') on live cloud — signerCalls == 1 + partialMapRetries and uidMisses == 0 hold across the previously flaky TEST_USER_1/prod matrix cell.

🤖 Generated with Claude Code

https://claude.ai/code/session_016rEFEXaZ9t3BftShqc9Y4B

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[github-actions]

Test Results

1 393 tests  +4   1 360 ✅ +4   3m 52s ⏱️ -59s
  206 suites ±0      33 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 9120c00. ± Comparison against base commit aea0c72.

[codecov]

Codecov Report

❌ Patch coverage is 95.83333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 29.85%. Comparing base (aea0c72) to head (9120c00).

Files with missing lines	Patch %	Lines
.../+cloud/+download/+internal/batchSignedUrlLookup.m	95.83%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #992      +/-   ##
==========================================
+ Coverage   29.79%   29.85%   +0.05%     
==========================================
  Files         857      857              
  Lines       43723    43750      +27     
==========================================
+ Hits        13029    13062      +33     
+ Misses      30694    30688       -6     

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