Context

PR #1966 removed the zeph-index dependency from zeph-tools to fix a same-layer violation. This required inlining tree-sitter language detection and grammar/query setup in search_code.rs.

Found by: impl-critic (IMP-03)

Problem

• Tree-sitter symbol queries are now duplicated between zeph-tools::search_code and zeph-index::languages
• This was an accepted trade-off to break the same-layer dependency, but creates drift risk
• If language queries are updated in one place but not the other, results will diverge

Possible approaches

1. Extract shared tree-sitter queries to zeph-common (Layer 0)
2. Create a thin zeph-treesitter crate at Layer 0 for shared grammar/query definitions
3. Accept the duplication and add a test that verifies query parity

Acceptance criteria

• Either single source of truth for tree-sitter queries, or automated parity verification
• Layered architecture preserved