Derive phone region from extracted location (locale-aware parsing)

[s-annam]

Problem

After Issue A, phone parsing uses a fixed US default region. But the résumé already tells us the candidate's region — extractContact extracts location in the same scan (src/lib/heuristics/extract-fields.ts:268, via US_LOCATION_RE / INTL_LOCATION_RE) — and we ignore it. A London or Bangalore résumé with a national-format number gets parsed as if US.

Use the extracted location as the region hint so national/local-format numbers parse and reformat correctly for the candidate's actual locale.

Approach

1. Add a small regionFromLocation(location: string): string | undefined helper (likely in phone.ts or a sibling): map US_LOCATION_RE matches → US; map the country tail of INTL_LOCATION_RE → ISO 3166-1 alpha-2 (e.g. United Kingdom→GB, India→IN, Canada→CA). Keep the country→ISO table small and explicit; unmatched → undefined.
2. Thread the derived region into the findPhoneNumbersInText / normalizePhone call from Issue A as defaultCountry.
3. Fallback to US when no location is extracted or the country is unmapped (matches the Issue A default — confirmed decision).

Depends on

Blocked by Issue A (the normalizer + findPhoneNumbersInText wiring must land first).

Affected files

• src/lib/heuristics/phone.ts (or sibling) — add regionFromLocation + country→ISO table.
• src/lib/heuristics/extract-fields.ts — pass derived region instead of hardcoded US.
• Tests — regionFromLocation unit tests (US + 2–3 intl); a fixture demonstrating an intl national-format number reformatting correctly.

Acceptance criteria

• regionFromLocation maps US + a small explicit set of intl countries to ISO codes; unmatched → undefined.
• Phone parsing uses the location-derived region; falls back to US when absent/unmapped.
• An international-locale fixture (national-format number) reformats to the correct national/international form.
• npm run test + npm run typecheck green.

Notes

Part of the phone-handling epic. Builds on Issue A.

[s-annam]

Implementation Complete — 12f23f8 (PR #100)

Acceptance Criteria

• regionFromLocation maps US + small intl set; unmatched → undefined — added in src/lib/heuristics/phone.ts with an explicit COUNTRY_TO_REGION table (GB/IN/CA/AU/DE/SG/…).
• Phone parsing uses location-derived region; falls back to US — extract-fields.ts now resolves location before the phone scan and passes regionFromLocation(location) ?? "US" into findFirstPhone().
• Intl national-format fixture reformats correctly — UK 020 7946 0958 → +44 20 7946 0958; GB/IN paths covered in phone.test.ts + extract-fields.test.ts.
• npm run test + npm run typecheck green — 407/407, typecheck clean.

Additional Changes

• mightHavePhone pre-filter relaxed for non-US regions (accept 7+ total digits). Required: national-format UK/Indian numbers have no + prefix and don't match the US-biased PHONE_RE, so they were dropped before libphonenumber saw them. US path unchanged.
• Ordering trap fixed: US_LOCATION_RE matches any 2-letter token after a comma (Manchester, UK → looks like a US state), so the intl country table is checked first; US-state fallback only on a country-table miss.

Closes on merge of #100.