chore: reduce accepted code-health debt

[sarthakagrawal927]

Summary

Reduce accepted code-health debt for #50 through behavior-preserving refactors. All 439 tests pass, typecheck clean, full quality gate green.

Changes

Complexity: 81 → 72 violations (−9)

extension/src/content.ts — 5 violations removed:

• Extracted textFromSelectors(...selectors) helper to replace ??-chains of textFromSelector calls in all scraper functions (scrapePersonio, scrapeWorkable, scrapeLinkedIn, scrapeSmartRecruiters, scrapeGeneric)
• Extracted firstScraperResult() to replace the 10-way ?? chain in scrape()

src/lib/local-storage.ts — 2 violations removed:

• Extracted optionalJobFields(j) helper shared by toJobApplication (CCN 29→5) and toSummary (CCN 21→3), splitting the ?? chains across two smaller functions

src/lib/evidence-mapping.ts (new) — 3 violations removed:

• Consolidated toEvidence, toPacketEvidence, toReplyEvidence — three near-identical row-to-evidence mappers — into a shared rowToEvidence(row, parseListFn, toImpactType) utility
• Each caller now passes its own list-parser and impact-type resolver

Duplication: 47 → 43 clones, 750 → 716 lines, 2.145% → 2.044%

• The evidence-mapping consolidation eliminated 4 clone groups (the three to*Evidence functions were triplicated code)
• Scraper refactors reduced structural duplication in content.ts

Baselines lowered

- complexity: { violations: 81, ... }
+ complexity: { violations: 72, ... }

- duplication: { clones: 47, duplicatedLines: 750, percentage: 2.1453702909122114 }
+ duplication: { clones: 43, duplicatedLines: 716, percentage: 2.044254104211278 }

Verification

• pnpm quality — full gate passes (check, typecheck, coverage, docs, extension typecheck, all 7 health checks)
• pnpm test — 439 tests pass
• No behavior changes: all refactors are extract-and-delegate, preserving exact semantics

Progress on #50