[test] Add unit tests for CommandHistory in @termuijs/core

[pranvxag]

What problem does this solve?

packages/core/src/history/CommandHistory.ts has no test file.
CommandHistory manages shell-style command history with navigation,
search, import/export, and size limits. None of this logic is currently
covered by tests, meaning regressions would go undetected.

Proposed solution

Create packages/core/src/history/CommandHistory.test.ts covering:

• add() ignores empty/whitespace-only commands
• add() stores valid commands in order
• add() evicts oldest command when maxSize is exceeded
• previous() navigates backward through history
• previous() clamps at first command
• previous() returns null when history is empty
• next() navigates forward through history
• next() returns null when past the last command
• search() filters commands case-insensitively
• getAll() returns a copy of all commands
• clear() empties history and resets index
• export() serializes history to JSON string
• import() restores history from JSON string

Which package would this belong in?

@termuijs/core — packages/core/src/history/CommandHistory.test.ts

GSSoC contributor?

• Yes. You contribute under GSSoC 2026 and want to work on this.
• No. You are filing a suggestion.

[github-actions]

✅ Auto-assigned to @pranvxag (issue opener).

Open your PR by 2026-06-29 (7 days). The bot frees this issue for another contributor after that date.

Reminders:

• ⭐ Star the repo first. The star-check job blocks your merge otherwise.
• PR title: type: short description
• Link this issue in your PR body: Closes #1748

Good luck. 🚀