Built-in structured output parser for CLI commands

Problem

When working with swamp model data from the CLI, structured output often needs post-processing — parsing JSON responses, extracting fields, filtering arrays. Currently users reach for python3 -c "import sys,json; ..." or jq one-liners piped after --json output, which is clunky and creates a dependency on external tools.

This comes up constantly when:

• Inspecting model data attributes from swamp data get
• Filtering output from swamp data list
• Extracting specific fields from swamp model method run results
• Chaining CLI commands where one step's output feeds the next

Proposed Solution

Ship a lightweight query/filter mechanism built into the swamp CLI itself. Options:

1. --query / -q flag on commands that emit JSON — a small expression language (CEL subset, jq-like path syntax, or JSONPath) to extract/filter fields inline. e.g.:

   • swamp data get dev-vms latest --json -q '.attributes.vms[].domain'
   • swamp data list dev-vms --json -q '.groups[].items[] | select(.name | contains("controller"))'

2. swamp query subcommand that reads JSON from stdin and applies an expression, so it can be piped:

   • swamp model method run dev-vms discover --json | swamp query '.data.attributes.vms | length'

3. Built-in --format templates for common extractions (table, csv, specific fields).

Since swamp already has a CEL evaluator for workflow expressions, reusing that for CLI output queries would be a natural fit and avoid adding a new expression language.

Alternatives

• Require users to install jq (common but not universal, especially on CI)
• Keep relying on python3 -c one-liners (verbose, error-prone)
• Do nothing (status quo works but adds friction to every CLI interaction)