Bound and time-limit workspace pattern regex extractors

[Widthdom]

Problem

src/CodeIndex/Indexer/Extensibility/ExtractorPluginRegistry.cs loads workspace pattern configs from .cdidx/patterns, and ConfiguredSymbolExtractor applies the configured regexes to source lines without an explicit timeout or pattern-count budget.

Impact

An untrusted or accidentally expensive regex can make indexing hang or consume excessive CPU across many files.

Expected

Bound pattern config size and count, compile regexes with a timeout or non-backtracking mode where possible, and surface rejected patterns clearly.

[Widthdom]

Work started on branch fix-issue2863-2864.