port(upstream#1931): remove dead relayTimes field

[adminopenclaw8-sketch]

"Split out of #25 (commit d205f468 there). This branch holds exactly one upstream change so it can be reviewed, tested and reverted on its own.\n\n## Upstream\n- PR: Kpa-clawbot/CoreScope#1931 by @Joel-Claw, merged 2026-09-02\n- Upstream commit: 4a776454ca96c36ba85f2ca807120f3ff0686a66\n- Applied with git cherry-pick -x onto master fda24ca5; upstream authorship kept, and the commit message carries the (cherry picked from commit …) line.\n- Patch-id identical to the #25 commit and to the upstream commit.\n- Scope: cmd/server/store.go (two lines).\n\n## Problem\nPacketStore.relayTimes was declared and allocated but never read or written.\n\n## Change\nRemoves the field and its make(). No behaviour change.\n\n## Adaptation to this fork\nNone. The cherry-pick applied without conflicts and the changed lines are identical to upstream.\n\n## Notes for review\nListed upstream as perf; it is dead-code removal, so no performance claim is made here.\n\n## Dependencies and merge order\n- Independent. Branched directly from master fda24ca5 and needs no other PR from this split.\n- A merge simulation of all 24 split PRs gives the same tree in upstream order and in reverse order.\n- The same simulation also merges cleanly with each of the open #11, #13 and #22, and with #33 (opened during this split; it makes TestPruneOldNeighborMetrics deterministic). If #33 lands first, the expected CI failure named below disappears; nothing in this PR depends on it.\n- Recommended position: 11 of 24, following upstream's merge order (the order #25 was assembled in).\n\n## Verification\nLocal run of the same commands as CI's “Go Build & Test” job (server tests with -race), on this branch and on master fda24ca5 under the same conditions (same machine, run one after another):\n\n| Check | master fda24ca5 | this branch | verdict |\n|---|---|---|---|\n| go-server-build-vet | PASS | PASS | |\n| go-server-test-race | PASS | PASS | |\n| channel-lib-test | PASS | PASS | |\n| decrypt-cli-build-test | PASS | PASS | |\n| dockerfile-copy-invariants | FAIL | FAIL | not runnable locally: script needs bash ≥4 (declare -A), macOS has 3.2; identical on master |\n| staging-disk-monitor | PASS | PASS | |\n| css-vars-lint | PASS | PASS | |\n\nBaseline failures (fail identically on master; not introduced or changed here): see rows marked baseline failure, unchanged.\n\nBrowser validation (local, fixture DB, no staging/production): Not applicable (no frontend change).\n\nNot run:\n- Playwright E2E suites (no local Playwright install); CI's E2E job will also be skipped, see below.\n- eslint (not installed locally; CI installs it on the fly).\n- Frontend JS suites (no frontend change).\n- Browser tests against staging/production (deliberately none).\n\nExpected GitHub CI: “Go Build & Test” is expected to fail on TestPruneOldNeighborMetrics, which already fails on master (see #25's run). Downstream jobs (Playwright, image build) are therefore skipped. “Deploy Staging” and all GHCR publish steps only run on push to master and cannot run for this PR.\nTwo further ingestor tests have failed intermittently in this split's CI on branches whose cmd/ingestor tree is byte-identical to master (#27, #28), so they can also appear here without being caused by this change:\n- TestBackfillTxLastSeen_ResolvesFromMaxObservationTimestamp: also reproduced locally on unmodified master.\n- TestMQTTStallWatchdog_DisconnectedEscalationThrottled_1749: the suite flake that upstream Kpa-clawbot#2003 (also split out of #25) addresses.\n\nGitHub CI result: run 34750406495 on 685b2f84. Go Build & Test: failure; all downstream jobs incl. Deploy Staging skipped. Failed tests:\n - TestPruneOldNeighborMetrics: fails on master, documented baseline\n\n🤖 Generated with Claude Code\n\n## Update — current master 693eb04 (2026-09-17)\n\nThe existing PR branch was updated without force-push from 685b2f84 to d1a80b2f. The merge graph preserves the original upstream-attributed commit, incorporates green master 693eb045dbb10ecdd4657444134a696f007297e1, and includes the verified local prep commit 0a30f1ac.\n\nThe PR diff against current master remains exactly cmd/server/store.go.\n\n### Fresh verification on d1a80b2\n\n- cd cmd/server && go test ./...: PASS (23.4 s)\n- git diff --check: PASS\n\nNo frontend, configuration, staging, production, deployment, workflow, or auto-merge action was performed. GitHub PR CI: run 35220090235 completed successfully. Go/build gates and Playwright E2E passed. The Docker job performed only the local staging build; GHCR login/push, release artifacts, staging deploy, and badge publication were skipped.\n\n"