fix(content-lane): split a scalar source field's multi-item block sequence per URL

[RealDiligent]

Summary

parseSimpleFrontmatter (src/review/content-lane/source-evidence.ts) collapses a block sequence to a comma-joined string, and for a scalar source field that value flows to scalarSourceUrlValues, which only knows how to split the flow ([a, b]) form. So a documentationUrl authored as a two-item block sequence yielded the single string "https://a.example/1, https://b.example/2". new URL() throws on that, so validateFetchableSourceUrl returns outcome: "invalid_url" → status: "hard_failure", blocking: true, the whole report "failed", and sourceEvidenceCloseDecision emits a "dead or invalid source URL" close/manual on a submission whose sources are both live.

The sibling list path (listSourceUrlValues) already splits each - item into its own SubmittedSourceUrl; only the scalar path collapsed. #8016's tests covered only the single-item sequence (a one-item join produces a valid URL), which is why this went undetected.

Fix

Add scalarSequenceItems(source, field), a small state machine over the raw frontmatter block (mirroring listSourceUrlValues' for..of + as string style) that returns one raw value per - item when the field is authored as a bare block sequence (field: with an empty inline value). The scalar-field loop uses it to emit one SubmittedSourceUrl per item. For every non-sequence form (an inline scalar, a flow [a, b] list, or a block scalar |/>) it returns null, so the existing parseSimpleFrontmatter + scalarSourceUrlValues reader is unchanged. A single-item sequence still yields exactly one URL with today's value, and a genuinely malformed value still hard-fails — the change removes a false positive without weakening the real check.

Tests

Added to test/unit/content-lane-source-evidence.test.ts:

• A scalar field carrying a two-item block sequence produces two SubmittedSourceUrl entries with the two distinct URLs.
• checkSubmittedSourceEvidence over that two-item field with a stub fetchImpl returning 200 for both reports status: "passed" (today: "failed" / invalid_url).
• The single-item sequence case is byte-identical to today.
• A genuinely malformed value (notaurl) still yields outcome: "invalid_url" / status: "hard_failure".
• Terminator coverage: a sequence ends at the next top-level key and at a blank line, an empty item is skipped, and an empty-valued field yields no URL.

The two multi-item cases fail against the current joined-string behaviour. Full file passes (94/94); local coverage of source-evidence.ts is 100% statements/branches/lines.

Closes #9668

[loopover-orb]

Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-29 20:15:46 UTC}

2 files · 1 AI reviewer · no blockers · readiness 100/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
The change correctly addresses the issue where scalar source fields authored as YAML block sequences were being collapsed into a single string, causing validation failures. The new `scalarSequenceItems` function properly splits block sequences into individual URLs, and the tests verify this behavior. The fix maintains existing validation logic while resolving the false positive for multi-item sequences.

Nits — 2 non-blocking

• The `scalarSequenceItems` function could benefit from more detailed comments explaining the regex patterns used for parsing block sequences.
• Consider adding a constant for the `9_` magic number used in the test cases to improve readability.

Decision drivers

• ✅ Code review — No blockers (1 reviewer)
• ✅ Gate result — Passing (No configured blocker found.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	✅ Linked	#9668
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 (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 251 registered-repo PR(s), 99 merged, 38 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	RealDiligent; Gittensor profile; 251 PR(s), 38 issue(s).
Improvement	✅ Minor	risk: clean · value: minor

Linked issue satisfaction

Addressed
The PR implements scalarSequenceItems to split multi-item block sequences into individual URLs, mirrors listSourceUrlValues' logic, and adds all required tests including regression cases for two-item sequences, single-item preservation, and invalid URL checks. The diff directly addresses the issue's core defect and all deliverables.

Review context

• Author: RealDiligent
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: Python, Ruby, TypeScript, Svelte, Cuda, JavaScript, Markdown, MDX
• Official Gittensor activity: 251 PR(s), 38 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Keep the PR focused and include validation evidence before maintainer review.

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.

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

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[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 79.37%. Comparing base (af98111) to head (0d1aa6b).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #9900       +/-   ##
===========================================
- Coverage   91.76%   79.37%   -12.40%     
===========================================
  Files         921      282      -639     
  Lines      113173    58785    -54388     
  Branches    27244     8686    -18558     
===========================================
- Hits       103854    46659    -57195     
- Misses       8034    11843     +3809     
+ Partials     1285      283     -1002     

Flag	Coverage Δ
backend	100.00% <100.00%> (+4.31%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/review/content-lane/source-evidence.ts	100.00% <100.00%> (ø)

... and 772 files with indirect coverage changes

[loopover-orb]

LoopOver approves — the gate is satisfied and CI is green.