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

• Add ConsoleFormatter.groupConsecutive() static method that groups consecutive messages with the same type, text, and argument count
• Add toStringGrouped() / toJSONGrouped() for count-aware formatting
• Add lastId to grouped output so consumers can access the last message in a group via get_console_message
• 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

• 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().
• lastId field: Enables consumers to access any message in a group. The first message's msgid is the group's ID, and lastId gives the range.
• 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, last msgid=5]

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)

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.