fix(author): require whole numeric values for factual grounding

[akoita]

Change

Author grounding previously accepted a numeric substring as evidence: a source containing 2020, 20.5, or 20% could support a claimed metric of 20. Citation completion and factual validation now share whole numeric-value matching, preserving decimal parts, percentage markers, magnitude suffixes, NFKC normalization, and case normalization. Exact years within date ranges remain supported.

Closes #300. This is a deterministic factual-safety correction for the v0.9.0 milestone; it does not resolve or explain the live pilot failures. #75 remains unvalidated and #250 remains blocked. The roadmap records that boundary and splits the affected observation history into readable paragraphs. No CLI, UI, or public contract changes require additional documentation.

Validation

• Eight partial-number regressions reproduced before the fix.
• Focused application checks: 5 files, 38 tests passed.
• pnpm install --frozen-lockfile, pnpm format, and VITEST_MAX_WORKERS=2 pnpm validate on Node 24.5.0 / pnpm 10.18.3.
• The initial full run passed 1,288 tests and timed out in one unrelated storage interruption test; that test passed in isolation (23 seconds), and all 54 release-script tests passed. The complete gate was rerun with reduced worker concurrency and unchanged timeout limits.
• No live providers or private candidate data used.