refactor(cli): default quota should-run to json

[huangruiteng]

Summary

• default only loopx quota should-run to JSON when no format is specified
• preserve explicit global --format and subcommand-local format precedence
• keep other no-format CLI commands on Markdown without TTY-dependent behavior

Validation

• pytest -q tests/test_cli_argument_diagnostics.py tests/control_plane/test_cli_output_budget.py (22 passed)
• ruff check on changed Python and tests
• loopx canary premerge --from-git-diff (standard tier, 4/4 selected canaries passed)
• public/private boundary scan on changed paths (clean)

[huangruiteng]

Pre-merge validation receipt for 7289260a:

• Changed surfaces: global CLI format resolution, quota should-run no-format output, explicit-format compatibility tests, agent-facing output-budget integration test.
• Focused tests: pytest -q tests/test_cli_argument_diagnostics.py tests/control_plane/test_cli_output_budget.py passed, 22/22.
• Static checks: Ruff passed on all changed Python paths; py_compile and git diff --check passed.
• Risk canary: loopx canary premerge --from-git-diff passed at standard tier. Selected and executed 4/4 catalog canaries: maintainability ratchet, CLI output budget regression, version-command modularization, and control-plane command modularization.
• Boundary scan: changed paths contain no credentials, private state, local absolute paths, internal links, or raw generated evidence.
• Failures/skips/manual holds: none.

Coverage is sufficient because the change is command-scoped and deterministic: parser-level tests prove the positive and negative default matrix plus explicit precedence, while the real CLI fixture proves no-format JSON and explicit Markdown end to end.