ci: bump the coverage-run matrix from 4 to 6 shards

[JSONbored]

Summary

• Bumps validate-tests's matrix from 4 to 6 shards (--shard=<i>/6), following up ci: shard the full-suite coverage run across a matrix #4815 now that real per-shard timing data exists.

Why

Measured from the 4-way rollout: ~2,026s of aggregate test+import work spread across 4 shards, landing at ~150s wall time each (~85% parallel efficiency), with ~35s of fixed per-shard overhead (checkout/cache/build-engine + upload steps). At 6 shards, that projects to ~135s (~2.2min) wall time per shard, cutting the overall CI critical path from ~3.5-4min down to roughly ~2.7-2.9min.

Deliberately not going straight to 8: checked this repo's actual concurrent-run history and found genuine bursts of 15-20+ simultaneous ci.yml runs (confirmed only 2 of 17 concurrent runs in one sampled burst were from my own session's retriggers -- the rest were other contributors'/automation's real traffic, mostly automatic push-to-main runs). Since each PR's shard phase multiplies the job-slots that run demands from the shared concurrent-runner pool, doubling shard count (4→8) doubles that per-run demand during exactly the bursts this repo already produces regularly -- risking queuing that could offset or reverse the wall-clock win. 6 shards is a smaller (1.5x, not 2x) step to validate before considering 8.

Test plan

• npx tsc --noEmit clean
• npm run actionlint clean
• YAML parses
• codecov-policy.test.ts / workflow-runner-labels.test.ts pass (no shard-count-specific assertions broke, only comment text updated)
• Watch real CI timing after merge, and watch for any shard jobs sitting queued rather than in_progress during a busy window -- that would be the signal to back off rather than push to 8

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.24%. Comparing base (65422c8) to head (9f0be78).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4944   +/-   ##
=======================================
  Coverage   94.24%   94.24%           
=======================================
  Files         444      444           
  Lines       38854    38854           
  Branches    14157    14157           
=======================================
  Hits        36617    36617           
  Misses       1577     1577           
  Partials      660      660           

Flag	Coverage Δ
shard-1	46.72% <ø> (-4.75%)	⬇️
shard-2	33.31% <ø> (-12.12%)	⬇️
shard-3	31.39% <ø> (-10.50%)	⬇️
shard-4	33.01% <ø> (-18.90%)	⬇️
shard-5	33.48% <ø> (?)
shard-6	45.20% <ø> (?)

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Warning

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⏸️ Gittensory review result - manual review recommended

_{Review updated: 2026-07-11 02:02:06 UTC}

2 files · 1 AI reviewer · 2 blockers · readiness 93/100 · CI green · unstable

⏸️ Suggested Action - Manual Review

• No linked issue detected — If this PR is intended to solve an issue, link it explicitly in the PR body.
• Maintainer requires a linked issue — Link the relevant issue (for example Closes #123) before opening the PR.

Review summary
This PR mechanically bumps the validate-tests shard matrix from [1,2,3,4] to [1,2,3,4,5,6], updating every shard-count reference in lockstep: the --shard=N/6 CLI arg, step display names, failure-guidance echo text, and prose comments describing the merge job's behavior. It's a pure CI/infra change confined to .github/workflows/ci.yml and a comment-only edit in test/unit/workflow-runner-labels.test.ts, with no src/** impact. The rationale is data-backed (real per-shard timing from the prior 4-shard rollout) and deliberately conservative (6 rather than 8, reasoned against this repo's observed concurrent-runner-pool contention), and CI already shows all six new shard jobs plus validate-tests-merge passing on this exact commit, confirming the merge/coverage-threshold step correctly consumes 6 shards' artifacts rather than silently assuming 4.

Nits — 3 non-blocking

• The description cites prior PR ci: shard the full-suite coverage run across a matrix #4815 as precedent rather than linking an eligible open issue — worth a one-line confirmation from the author per repo convention, though this is narrow operator-facing CI tuning rather than a feature addition.
• The test plan leaves 'watch real CI timing after merge / watch for queued shard jobs' unchecked as a stated follow-up — not blocking, but worth tracking so the post-merge validation isn't lost.
• Once merged, capture the observed 6-shard wall-clock number in a follow-up comment or issue so the eventual 6→8 bump has the same empirical grounding this PR used for 4→6.

Concerns raised — review before merging

• No linked issue detected — If this PR is intended to solve an issue, link it explicitly in the PR body.
• Maintainer requires a linked issue — Link the relevant issue (for example Closes #123) before opening the PR.

Signal	Result	Evidence
Code review	❌ 2 blockers	1 reviewer
Linked issue	⚠️ Missing	No linked issue or no-issue rationale found.
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (no linked issue context).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 48 registered-repo PR(s), 40 merged, 312 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	JSONbored; Gittensor profile; 48 PR(s), 312 issue(s).
Gate result	❌ Blocking	Repo-configured hard blocker found.

Review context

• Author: JSONbored
• Role context: owner (maintainer lane)
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 48 PR(s), 312 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Treat this as maintainer-lane context rather than normal contributor-lane activity.
• Explain no-issue PR.
• Link the issue being solved, or explicitly explain why this is a no-issue PR.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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