docs(investigations): retry-serial #676 smoke-test — static path + HOLD rationale

[jsboige]

What

Delivers the smoke-test investigation for the retry-serial fix #676 (issue #613 Option C), per dispatch #98vo07 primary. Closes the primary item with a static path analysis + HOLD rationale + post-tag validation plan.

Why a doc, not a runtime run

The retry path fires only when (1) ContinueOnHarvestSetFailure=true, (2) HarvestSetRetryAttempts>0, and (3) at least one set actually failed in the parallel loop. Condition (3) is non-deterministic (depends on a real timeout under parallelism) — a clean run fires zero retries, proving nothing about the retry path itself. Forcing a deterministic timeout requires either a full release regen (HOLD until tag) or a synthetic-timeout harness (out of smoke-test scope). The doc is the honest deliverable pre-tag.

Contents

• §2 Static path analysis — 3 config guards (ContinueOnHarvestSetFailure L45, HarvestSetRetryAttempts L55, HarvestSetRetryBackoffSeconds L62) + the seam HarvestImages L88–L128 with exact line refs.
• §2.3 Re-render correctness — why retry doesn't double-generate: a failed set never added its key to the dictionary (ContainsKey guard in ProcessLocalizedHarvest), so the retry re-renders from scratch; successful sets keep their key → skipped.
• §2.5 Trigger conditions — the 3 guards, including the non-deterministic one.
• §3 HOLD rationale — régén complète HOLD + non-determinism of timeout-under-parallelism.
• §4 Deterministic coverage — cross-ref to PR test(harvest): pin RetryAsync contract (#613 DoD gap) #678 (8 RetryAsync unit tests, green) covering the retry/backoff contract.
• §5 Post-tag validation plan — capture [HARVEST-RETRY] logs at the next release regen; metrics to report (sets entering retry, recovered, residual, timing).
• §6 fix(harvest): spectre [HARVEST-FAILURE] interprété comme markup couleur → InvalidOperationException fatale (tue #614) #630 interaction — fatal-path bug that bypasses the retry; fix(logger): #630 escape Spectre markup on all console paths + non-throwing render fallback #655 (03/07) is the fix candidate to verify post-tag.

Scope

Pure documentation (.md), no code/runtime/2sxc/DNN surface — not subject to the #596 runtime-pending gate. Companion to #678 (RetryAsync unit tests) and #676 (the merged fix).

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