Introduces a standalone src/filter_parser.rs module (no dependency on
engine/index types) that parses the FilterBar query language into a
FilterExpr AST using a pest grammar (src/filter_parser.pest). Supports
regex("...") searches, metric_name[param] <op> value comparisons,
reserved sequence/timestamp metrics, and and/or combinators with
correct precedence (and binds tighter than or) and parenthesized
sub-expressions. Evaluation against real log data is left to a later
integration ticket.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o
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