Fix Cursor tool-call normalization duplicates

[V3RON]

Summary

• validate the bug against a real Cursor Agent run: the raw session.stream.jsonl emitted both tool_call.started and tool_call.completed for one shell invocation, while normalization produced duplicate downstream command events
• make Cursor normalization subtype-aware by keeping completion results but deduplicating command, file-read, and skill-signal extraction per logical call id
• add regression coverage so started/completed pairs only emit one normalized tool call, one command, and one file read

Validation

• real Cursor repro before fix: raw artifact contained one logical shell call split into tool_call.started and tool_call.completed, while normalized output contained two command events
• real Cursor repro after fix: raw artifact still contains both subtypes, while normalized output now contains one toolCall, one command, and one toolResult
• repro artifacts used during validation live under /var/folders/tb/j39z273s5kn7lb9tz1dhk8l00000gn/T/opencode/issue-24-cursor-repro*

Testing

• npm test -- test/adapters/cursor-agent.test.ts test/limits/max-steps.test.ts
• npm run typecheck

Closes #24.