Add Format::Truncated — enforce maximum byte size on serialized output

[ioquatix]

Summary

Adds Console::Format::Truncated, a format wrapper that enforces a maximum byte size on serialized log output.

If the serialized record exceeds the limit, top-level fields are replaced with "[TRUNCATED]" one at a time, largest first, until the record fits within the budget. If truncating every field is still insufficient, a minimal {"truncated":true} fallback is returned.

Design

• Single serialization pass — @format.dump is called exactly once. All truncation is done by direct byte-range surgery on the already-serialized string; no Ruby objects are re-allocated or re-serialized.
• Shallow JSON parser — a hand-rolled scanner (parse / scan_string / skip_value / skip_whitespace) locates top-level key→value byte ranges. It handles JSON whitespace correctly and is robust against any conformant JSON serializer, not just JSON.dump's compact output.
• Largest-first replacement — fields are replaced in descending size order so the minimum number of fields are truncated.
• Truncation flag — a ,"truncated":true fragment is injected before the closing } so consumers can detect that the record was modified.

Usage

format = Console::Format::Truncated.new(Console::Format::Safe.new)
# or with a custom limit:
format = Console::Format::Truncated.new(Console::Format::Safe.new, maximum_size: 4096)

Files

• lib/console/format/truncated.rb — implementation
• lib/console/format.rb — added require_relative "format/truncated"
• test/console/format/truncated.rb — 7 tests covering pass-through, largest-first truncation, multi-field truncation, skip-if-replacement-is-larger, fallback, and default size behaviour