feat!: Key enum redesign — grouped bases, 138 keys, KeyFromString

[kolkov]

Summary

• Key enum redesign: flat iota (94 keys) → grouped explicit bases (138 keys)
• 12 grouped const blocks with reserved gaps (net/http pattern)
• 44 new keys: F13-F24, Media, Volume, Browser, System, International
• KeyFromString() thread-safe reverse lookup (sync.Once)
• W3C UIEvents naming convention

BREAKING

Key numeric values changed. Pre-v1.0 — no external consumers store numeric values. This is the last chance to renumber before v1.0 stability commitment.

Enterprise references

• SDL3: USB HID explicit values
• Qt6: hex grouped explicit values (0x01000000+ prefix)
• Flutter: USB HID code-generated
• Go net/http: explicit grouped values (100, 200, 300...)
• All use explicit values with grouping. None use flat sequential.

Test plan

• go test ./... — 87 tests pass
• golangci-lint run — 0 issues
• Cross-platform build (linux, darwin)
• Downstream: gogpu builds clean
• Key group boundaries verified (no overlap)
• String ↔ KeyFromString round-trip for all 138 keys

[codecov]

Codecov Report

❌ Patch coverage is 99.33110% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
events.go	99.33%	1 Missing and 1 partial ⚠️

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