Add `--json` output flag to read commands

[ewega]

Problem

All CLI output is human-formatted (emoji, Unicode box-drawing, banners). There is no machine-readable output mode. This blocks two scenarios:

1. Agent consumption — coding agents (Copilot CLI agent, Claude, etc.) cannot reliably parse CLI output to take follow-up actions
2. Scripting — users who want to pipe gh devlake output into jq, dashboards, or automation scripts must screen-scrape

The Playwright CLI demonstrates the pattern: CLI commands return structured snapshots to stdout that agents consume directly. For gh-devlake, the equivalent is structured JSON from read commands.

Proposed Solution

Add a --json flag (or --output json) to all read-only commands. When set:

• Suppress emoji, banners, box-drawing, and interactive prompts
• Print a single JSON object to stdout
• Exit with code 0 on success, non-zero on error (with JSON error body)

Commands to update

Command	JSON output shape
status	{ deployment: {…}, endpoints: [{name, url, healthy}], connections: [{plugin, id, name, healthy}], projects: [{name, blueprintId}] }
configure connection list	[{id, plugin, name, endpoint, organization, enterprise}]
configure scope list (from #55)	[{scopeId, name, fullName, plugin, connectionId}]
configure project list (from #56)	[{name, description, blueprintId}]

Implementation approach

1. Add a package-level outputJSON bool flag on rootCmd.PersistentFlags() so it's available to all commands
2. Create a helper func printJSON(v any) error in cmd/helpers.go that marshals and writes to stdout
3. Each command's RunE checks outputJSON early and branches to a JSON code path that builds a struct and calls printJSON
4. Human output remains the default — no behavioral change for interactive users

Example

# Human (default)
$ gh devlake status
╭──────────────────────────────────────────────╮
│  DevLake Status                              │
╰──────────────────────────────────────────────╯
  ✅ Backend API: http://localhost:8080
  ...

# Machine
$ gh devlake status --json
{"deployment":{"method":"local","stateFile":".devlake-local.json"},"endpoints":[{"name":"backend","url":"http://localhost:8080","healthy":true}],"connections":[{"plugin":"github","id":1,"name":"GitHub - my-org","healthy":true}]}

Acceptance Criteria

• --json flag available on status, configure connection list
• --json flag ready for configure scope list (configure scope add/list/delete: Add CRUD subcommands for scope management #55) and configure project list (configure project add/list/delete: Add CRUD subcommands for project management #56) when they land
• JSON output is a single line (no pretty-print by default) for easy piping
• No emoji, banners, or interactive prompts in JSON mode
• Error responses are also JSON: {"error": "message"}
• go build ./... and go test ./... pass

Target Version

v0.4.x — Foundation for agent-friendly CLI and AI features.

References

• Playwright CLI pattern: microsoft/playwright-cli — commands return structured output that agents consume via stdout. See the snapshot mechanism where each command emits a parseable snapshot.
• cmd/status.go — current human-formatted status output
• cmd/configure_connection_list.go — current human-formatted connection list
• cmd/helpers.go — printBanner() and other output helpers
• configure scope add/list/delete: Add CRUD subcommands for scope management #55 — configure scope list (will need --json support)
• configure project add/list/delete: Add CRUD subcommands for project management #56 — configure project list (will need --json support)