Wave 0: Search crate foundation, traits, and CLI skeleton

[leesharon]

Overview

Create the crates/rskim-search/ crate with public API types, core traits, and CLI subcommand skeleton.

What to Build

New crate: crates/rskim-search/

• Cargo.toml depending on rskim-core, thiserror, serde, serde_json, anyhow, rayon
• src/lib.rs — public API re-exports (~50 lines)
• src/types.rs — core types (~150 lines):
  • SearchResult { file_path, line_range, score, matched_field, snippet, match_positions }
  • SearchField enum: TypeDefinition, FunctionSignature, SymbolName, ImportExport, FunctionBody, Comment, StringLiteral
  • SearchQuery { text_query, ast_pattern, temporal_flags, limit, offset }
  • IndexStats { file_count, total_ngrams, index_size_bytes, last_updated }
  • SearchError enum (thiserror, following SkimError pattern)
• src/traits.rs — core traits (~100 lines):
  • SearchLayer: fn search(&self, query: &SearchQuery) -> Result<Vec<(FileId, f32)>>
  • LayerBuilder: fn add_file(&mut self, path, content, lang) -> Result<()>; fn build(self) -> Result<Box<dyn SearchLayer>>
  • FieldClassifier: fn classify_node(&self, node, source) -> SearchField

Modify existing files

• Cargo.toml (workspace root, line 2): add "crates/rskim-search" to members
• crates/rskim/Cargo.toml: add rskim-search dependency
• crates/rskim/src/cmd/mod.rs (line 33): add "search" to KNOWN_SUBCOMMANDS
• crates/rskim/src/cmd/mod.rs (line 275+): add routing in dispatch()
• crates/rskim/src/main.rs (line 45): update is_flag_with_value() for --build, --rebuild, --update, --ast, --blast-radius, --limit
• Create crates/rskim/src/cmd/search.rs with help text and stub

Dependencies

None — this is the root of the dependency graph.

Acceptance Criteria

• cargo check passes for workspace with new crate
• skim search --help prints help text
• skim search "test" prints "not yet implemented" to stderr
• Core types and traits compile with no warnings
• At least 3 unit tests for type construction/validation

Implementation Guidelines Checklist

• No file exceeds 400 lines
• Every public function has /// doc comment
• All dependencies injected
• All fallible operations return Result<T, SearchError>
• Module has #[cfg(test)] mod tests with: happy path, edge case, error path
• No hardcoded language-specific match arms
• New types derive Debug, Clone minimum