test: expand URL state tests with edge cases and round-trips

[NewCoder3294]

Summary

Expands tests/urlState.test.mts from 8 tests (3 suites) to 70 tests (16 suites) covering comprehensive edge cases for parseMapUrlState and buildMapUrl.

New test categories (62 new tests across 13 new suites):

parseMapUrlState edge cases:

• Empty/missing input (2 tests) — empty string, bare ?
• Country validation (7 tests) — invalid codes, lowercase normalization, empty, single char, digits, URL-encoded, whitespace trimming
• Zoom boundaries (8 tests) — 0, -1, 25, NaN, Infinity, -Infinity, fractional, non-numeric
• Lat/lon boundaries (10 tests) — valid extremes (90/180), out-of-bounds clamping, NaN, independent parsing
• TimeRange validation (6 tests) — valid values, invalid "99h", empty, arbitrary string, case mismatch
• View validation (3 tests) — valid value, invalid value, empty
• Layer parsing (7 tests) — selective enable, unknown names ignored, "none", empty, absent, extra commas, whitespace
• Duplicate params (2 tests) — first-value-wins for country and zoom
• Missing ? prefix (1 test) — params without leading ?

buildMapUrl edge cases:

• Default/minimal URL (4 tests) — null center, no country, layers=none, required params present
• All parameters set (1 test) — full URL with every param
• Center edge cases (2 tests) — undefined center, 4-decimal formatting

Round-trip tests:

• Parameter round-trips (9 tests) — every view value, zoom, lat/lon precision, all timeRange values, country, expanded, multiple layers, layers=none, complex state with all params

Test plan

• All 70 tests pass with node --import tsx --test tests/urlState.test.mts
• Type checks pass (pre-push hook)
• CI should confirm green on this branch

🤖 Generated with Claude Code

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