perf: optimize entire core codebase functions and tighten regression tests

[DevvGwardo]

Summary

This PR applies a full optimization pass across Peppy core functions and hardens key unit tests.

What changed

Core runtime optimizations

• peppy/cache.py

  • Improved cache robustness with stronger hashing and freshness behavior.
  • Better handling for cache reads/writes in hot paths.

• peppy/indexer.py

  • Faster ignore/path filtering and improved indexing throughput behavior.
  • Better worker utilization strategy and metadata handling.

• peppy/searcher.py

  • Added bounded symbol search flow with early stopping support.
  • Improved file-pattern/path matching behavior.
  • Improved grep execution path and context generation overhead.

• peppy/parsers.py

  • Corrected symbol traversal/classification edge behavior to improve extraction quality.

• peppy/interface.py

  • Reduced repeated work in symbol lookup/overview pathways.
  • Better propagation of search limits into lower-level search calls.

• peppy/server.py

  • Improved search tool parameter flow and response behavior for optimized search execution.

• pyproject.toml

  • Updated script/runtime wiring to align with optimized runtime entry flow.

Test hardening

• tests/unit/test_parsers.py

  • Fixed weak/no-op assertions and replaced with meaningful checks.

• tests/unit/test_searcher.py

  • Added/updated assertions for bounded symbol search behavior.
  • Added regression coverage for relative file path lookup behavior.

Why

• Improve end-to-end performance for indexing and search-heavy usage.
• Fix correctness edge cases discovered during review.
• Raise confidence via stronger unit test assertions.

Notes

• Changes are backward-compatible and focused on optimization/correctness.
• This PR is designed to be mergeable independently from prior optimization PRs.