Module exec 

Exec runtime: build argv from a parsed pipeline and execute it as a chain of child processes. No shell is ever invoked.

The pipeline AST itself is produced by crate::parse::exec; this module is concerned only with executing it safely.

Semantics:

• A ValueRef is resolved against an ExecContext (query/path/header/ var maps and a BodyValue).
• A Text token is always emitted as one argv element. Missing interpolations render as the empty string.
• A [..] Group token is emitted only if every required interpolation resolves; otherwise the whole group is omitted from argv (this is how optional flags work).
• Pipeline stages are wired stdin → stdout. A bare Source stage ($ | cmd) feeds a value as stdin to the next command.

Structs

ExecContext

ExecOutput

Enums

BodyValue

Functions

build_argv

preview_pipeline

Render a human-readable, non-executing preview of pipeline against ctx. Used by --dry-run to log the commands that would have run.

run_pipeline