feat: group identical consecutive console messages in list_console_messages

[masamaru0513]

Summary

Group consecutive identical console messages in list_console_messages, similar to Chrome DevTools' console grouping behavior.

Fixes #904

Changes

• Introduce GroupedConsoleFormatter subclass that extends ConsoleFormatter and overrides toString() / toJSON() for count-aware formatting
• Add ConsoleFormatter.groupConsecutive() static method that groups consecutive messages with the same type, text, and argument count
• Apply grouping before pagination so grouped counts are accurate and page sizes reflect the collapsed view
• Add unit tests for grouping logic, string formatting, and JSON output

Key design decisions

• GroupedConsoleFormatter subclass: Keeps the existing formatter interface clean — no new methods added to ConsoleFormatter. ConsoleFormatter and GroupedConsoleFormatter are interchangeable via the same interface.
• Grouping before pagination (not at format time): This was the feedback on feat(console): group consecutive identical console messagesfeat(console): group consecutive identical console messages #963 and Group identical console messages in list_console_messages #1025 — grouping at format time breaks pagination counts. This implementation groups in McpResponse before calling paginate().
• No lastId: Since grouped messages are truly identical, only the first message's ID is needed.
• argCount matching: Prevents false grouping of messages with the same text but different argument counts.

Output example

msgid=1 [log] hello world (1 args) [5 times]

Testing

• Unit tests in tests/formatters/ConsoleFormatterGrouping.test.ts
• Manual verification: identical messages (×5), mixed pattern (A,A,B,A,A → A×2, B×1, A×2)

[masamaru0513]

@OrKoN
Refactored as suggested, here's a summary of the changes:

• Introduced GroupedConsoleFormatter subclass that overrides toString() / toJSON()
• Dropped lastId; only the first message's ID is used
• No new methods added to the formatter interface
• ConsoleFormatter and GroupedConsoleFormatter are interchangeable via the same interface

Ready for another look when you get a chance. Thanks!

[OrKoN]

Please update the PR description accordingly.

[masamaru0513]

@OrKoN
Updated the PR description. Sorry about that.

[OrKoN]

Thanks!