Content search tool.

Searches file contents using regex patterns. Uses ripgrep (rg) when available for performance, falls back to pure Elixir regex.

Sandbox exemption

ripgrep is spawned with System.cmd/3, outside NetRunner, and is deliberately not confined by Nous.Sandbox. This is the documented exception to "NetRunner is the single execution path". The reasoning:

• Neither provider restricts reads. Seatbelt's profile is (allow default) (deny file-write*) and bwrap binds / read-only, so confining a process that only ever reads adds exactly zero enforcement.
• The argv is already hardened: the pattern goes through --regexp and a -- terminator ends option parsing before the positional path, and the environment is scrubbed via Nous.Tools.Env.scrubbed_overrides/0.
• The environment is genuinely scrubbed rather than merged: Erlang's {env, _} option adds to the inherited environment, so the allowlist is passed as scrubbed_overrides/0, which also emits {name, false} for every other currently-set variable and thereby actually unsets it.
• Every matched path is re-validated through Nous.Tools.PathGuard before it reaches the caller.
• Nous.Sandbox fails closed, so routing this tool through it would delete a working read-only search tool on every host with no provider installed — for no security gain whatsoever.