fix(research): keep decimals intact when splitting citation claims

[vishnujayvel]

What & why

buildCitationGraph splits synthesis text into claims with a regex that treats every . as a sentence boundary. Decimal amounts in the report ($62.3 billion, 27.7 percent) were therefore cut mid-number, so citation_graph[].claim started after the decimal ("3 billion...", "7 percent...") while the report body itself stayed correct.

Fixes #274.

Credit: @oQAQo1 for the repro and root-cause analysis (sentence split at digit.digit in src/research/citation-graph.ts).

Changes

• A digit-flanked . is no longer treated as a sentence boundary, so decimal numbers stay inside the claim.
• Regression tests cover a single decimal, multiple decimals in one sentence, and correct multi-sentence splitting.
• Abbreviations (e.g., U.S.) remain a known limitation of this splitter (out of scope for this fix).

Testing

• npx vitest run tests/unit/research/citation-graph.test.ts passes (14 tests)
• npx tsc --noEmit passes
• Added/updated tests for the new behavior
• Revert-proof: with the src change stashed, the new tests fail with claim text starting mid-number ("3 billion in Q4 FY2026..."), matching the issue symptom

Checklist

• Follows Conventional Commits
• Focused change (no unrelated refactoring)
• I have read CONTRIBUTING.md and agree to its contribution terms

Summary by CodeRabbit

• Bug Fixes

  • Improved sentence splitting to preserve decimal values, preventing periods in numbers from being treated as sentence breaks.
  • Maintained accurate citation mapping and confidence information across sentences containing multiple decimal values.

• Tests

  • Added regression coverage for decimal numbers in citation claims and multi-sentence content.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 88db79c2-0bf7-4ee6-9204-4c2da2408814

📥 Commits

Reviewing files that changed from the base of the PR and between b3ccf92 and db9df57.

📒 Files selected for processing (2)

• src/research/citation-graph.ts
• tests/unit/research/citation-graph.test.ts

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📝 Walkthrough

Walkthrough

The citation graph sentence splitter now preserves decimal values. Regression tests verify complete claims, correct sentence boundaries, source-index mappings, and confidence levels for decimal-containing research synthesis text.

Changes

Citation decimal handling

Layer / File(s)	Summary
Decimal-safe sentence splitting and regression coverage src/research/citation-graph.ts, tests/unit/research/citation-graph.test.ts	The sentence matcher no longer splits on periods between digits. Tests verify single and multiple decimal values, sentence separation, source indices, and confidence levels.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes preserving decimal values during citation-claim sentence splitting.
Linked Issues check	✅ Passed	The implementation and regression tests address issue #274 by preserving decimals and maintaining sentence splitting, source mapping, and confidence behavior.
Out of Scope Changes check	✅ Passed	All changes support the linked issue and PR objective; the abbreviation note and focused regression tests are directly relevant.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[vishnujayvel]

Thanks for the review, and for independently probing $62.3 / 27.7 / $5.8 and
Version 1.2.3 shipped yesterday [1]. rather than taking the test file's word for it.

To restate the limitation plainly so it isn't lost if this gets revisited: abbreviations
(e.g., U.S.) still fragment. That is pre-existing behaviour, unchanged by this PR, and fixing
it needs an abbreviation list rather than a lookaround — a different change with a different risk
profile. Happy to open a follow-up issue for it if you'd find that useful.

[vishnujayvel]

Thanks @Frankie-Xu for the careful reviews and re-verification — and for confirming the e.g./U.S. fragmenting is a pre-existing limitation rather than a regression from this change.

[KnockOutEZ]

Hi @vishnujayvel — thank you for this PR, and I'm sorry it's been sitting here without a proper review.

I've been heads-down building some pretty big features and improvements for wigolo, and as a solo dev, shipping that while also reviewing and maintaining every issue and PR has been genuinely hard. This one isn't forgotten — it just hasn't had the attention it deserves yet.

I'd really appreciate your patience here. I'm going to work through the open PRs and issues properly over the next few weeks (sooner if I can free up), and I'll follow up right here.

In the meantime, the wigolo Discord is open if you'd like to follow what's being built, ask questions, or nudge me directly: https://discord.gg/BkUUgz2bNF

Thanks again for contributing, and for understanding — it genuinely means a lot. 🙏