v0.3.0

Two strands: giving an operator control over what the server sees and what it
may do, and a documentation pass aimed at readers who have never seen the
project.

Configuration

• Per-root .project-lens.json contributes exclude patterns for that root only,
  unioned with the global exclude. Never applies to a sibling root.
• exclude is the only key that file may set. It lives inside a scanned tree,
  so roots and allow_writes are ignored there by design: a cloned repository
  must not be able to widen the scan or enable writes. Malformed fails startup.
• allow_writes option with PROJECT_LENS_ALLOW_WRITES override. write_file and
  scaffold_project are not registered unless set, so a client that connects
  without them cannot call them.
• Stricter schema validation in loadConfig for exclude and allowWrites.

Benchmarks

• Scenarios labelled stable vs unstable, so non-reproducing results are marked
  rather than published beside ones that reproduce.
• Token cost separates default-session from write-enabled schema sets, and
  reports framing overhead and schema break-even directly.
• search gains a scope: "all" scenario; redundant percentiles dropped.

Tests

• 100% coverage across affected modules; new withFakeRg helper for ripgrep
  failure paths.
• Integration tests assert write-tool absence from the tool list, not just
  call refusal. Different guarantees, and only the former is what the security
  model claims.

Documentation

• README rewritten for a cold reader: what it is and why, reference material
  folded into collapsible sections, install routes and client registration
  recipes for Claude Code, Codex CLI, Gemini CLI and generic JSON clients.
• New CONTRIBUTING.md: setup, layout, design invariants, testing and
  benchmarking guidance, commit conventions, patch submission.