[None][fix] Preserve KV transfer outcomes independently of polling

[chienchunhung]

Summary

Commit each native KV-transfer Attempt's logical outcome when the task/session changes state, rather than when it is first polled. A later cancellation, failure, or physical completion cannot rewrite an earlier Delivered/Failed/Cancelled result. Physical retirement and deadlines are unchanged.

Major changes

• _LogicalOutcomes: serialize completion against session failure/cancellation; preserve original cause and local/peer cancellation origin.
• TaskHandle.poll(): observe the committed outcome while keeping report progress separate.
• Regression tests: cover early/late/fresh observers, queued cancellation, sibling outcomes, original errors, and scatter/cancel ordering.

Verification

• Test-first commit 7d0430794e, with current-main production code: 14 intended failures / 30 passes. The following fix commit passes the expanded suite.
• TaskHandle coverage: 27 → 55 cases (+28); TaskHandle/fetch/publish suites: 48 → 76 cases, all passing. These are test counts, not line-coverage percentages.
• Expanded local checks: 192 passed, 1 skipped, 4 excluded. These ran on macOS with a source-only dependency-stub harness, not native TRT-LLM/NIXL/CUDA. The four executor-fixture exclusions also fail in that harness on baseline.
• Native CPU CI at this head: 55/55 TaskHandle cases and 76/76 TaskHandle/fetch/publish cases passed on each of x86 and ARM, including all 28 added cases.
• Full CI #61068 (helper #74244): FAILURE — 61,513 passed / 24 failed / 12,113 skipped. Failures are executor/KV-manager fixture AttributeErrors outside this patch: 20 leaf failures currently waived under NVBUG 6800223 / [None][fix] Initialize KV cache fixtures and unwaive nine cases on all platforms #19382, plus four failing suite wrappers. The focused suites above are green; the full pipeline is not.
• Ruff lint/format, diff checks, GitHub pre-commit, and separate iterative self-review are clean.

Based on main@e72f70e99d. Size: 208 production + 318 test lines changed.

[chienchunhung]

/bot run --disable-fail-fast

[tensorrt-cicd]

PR_Github #74244 [ run ] triggered by Bot. Commit: 8b20e04 Link to invocation

[tensorrt-cicd]

PR_Github #74244 [ run ] completed with state FAILURE. Commit: 8b20e04
/LLM/main/L0_MergeRequest_PR pipeline #61068 completed with status: 'FAILURE'

CI Report

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CI Agent Failure Analysis

Link to invocation