feat(element-template): add --values-file for batch property input on apply

[Copilot]

Repeating --set name=value for every property is unwieldy for templates with many fields (e.g. AI Agent connectors). --values-file accepts a JSON object mapping binding names to values as a batch alternative.

Usage

c8ctl element-template apply -i io.camunda.connectors.agenticai.aiagent.jobworker.v1 \
  Activity_1 diagram.bpmn \
  --values-file agent-config.json

{
  "systemPrompt": "=context.prompt",
  "model": "gpt-4o",
  "maxTokens": "4096"
}

Use --values-file - to read from stdin (BPMN must then be a file path):

jq -n --arg url "$API_URL" '{"method":"POST","url":$url}' \
  | c8ctl element-template apply -i io.camunda.connectors.HttpJson.v2 Task_1 process.bpmn \
    --values-file -

--set overrides --values-file when both target the same property. Numbers and booleans in the JSON are coerced to string automatically.

Changes

• helpers.ts — ParsedPluginArgs gains valuesFile: string | null; parseArgs handles --values-file/--values-file=; new readValuesFile async helper reads JSON from file or stdin and emits name=value strings compatible with the existing --set pipeline
• commands/apply.ts — merges values-file args before --set args (so --set wins on conflict); guards against simultaneous stdin use for both values and BPMN
• c8ctl-plugin.ts — adds "values-file" flag declaration, updated help description and examples
• README.md — documents --values-file with file and stdin usage examples
• element-template.test.ts — 11 new tests: file-based values, --set override precedence, --values-file= form, error paths (invalid JSON, non-object, missing file, missing arg), stdin usage, and the stdin conflict guard