Searches files using powerful regex matching.

- Supports Rust regex syntax (RE2-style — no lookaround or backreferences). Use line anchors or post-filters instead of (?!…)/(? {{#if IS_HL_MODE}} - Text output emits a file snapshot tag header per matched file plus numbered lines: `¶src/login.ts#1f`, `*42:if (user.id) {` (match), ` 43:return user;` (context). Copy the header for anchored edits; ops use bare line numbers. {{else}} {{#if IS_LINE_NUMBER_MODE}} - Text output is line-number-prefixed {{/if}} {{/if}} - You MUST use the built-in `search` tool for any content search. NEVER shell out to `grep`, `rg`, `ripgrep`, `ag`, `ack`, `git grep`, `awk`, `sed`-for-search, or any other CLI search via Bash — even for a single match, even "just to check quickly", even piped through other commands. - Bash `grep`/`rg` loses `.gitignore` semantics, bypasses result limits, and wastes tokens. The `search` tool is faster, structured, and already wired into the workspace — there is no scenario where Bash search is preferable. - If you catch yourself typing `grep`, `rg`, or `| grep` in a Bash command, stop and re-issue the lookup through the `search` tool instead. - If the search is open-ended, requiring multiple rounds, you MUST use the Task tool with the explore subagent instead of chaining `search` calls yourself.