feat(id): add kitty-disambiguate-v1 key decoding - #4438

Summary

 Key.parse                 # unchanged legacy behavior
+Key.parse_events          # rich keys, modifiers, and Press events
+Key.to_legacy             # project only representable meanings
+kitty-disambiguate-v1 reference + shared fixtures

Slice A of #787 only. The decoder is additive and inert: no negotiation, SSH/browser activation, or session changes. Numeric forms, modifier encoding, and functional-key entries were verified against the upstream kitty keyboard protocol on 2026-11-02.

Evidence

• Before: just roc-test — Key had 13 legacy expectations and no rich decoder.
• After: just roc-test — RocJson 29, Screen 15, Key 59 expectations pass; fixture JSON parses; git diff --check clean.
• Existing Key.parse expectations, including modified-arrow Unknown, remain unchanged.

Merge Danger

Door: two-way

Blast Radius: low

New API and fixtures only; active behavior remains unchanged. Unsupported protocol forms remain Unknown. Later activation slices remain gated on F13.4 detection (#786).

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