The Claude Code CLI doesn't support --max-tokens. This caused the CLI
backend to always fail with exit code 1. Also adds args validation tests
for both claude and codex CLI backends.
Change-Id: I57c5cc672ed08de291e3941511ce68ba56e5b4ff
Replaces the monolithic modules.test.js (983 lines) with focused
per-module test files sharing a common test-setup.js. Each file is
under 225 lines. All existing test assertions preserved.
New files: test-setup.js, anchor.test.js, schema.test.js, cache.test.js,
cards-nav.test.js, markdown.test.js, vault-batch.test.js, i18n.test.js,
scroll.test.js, settings.test.js, providers.test.js, streaming.test.js,
cli.test.js
Change-Id: I37a3342a1588807277e679e6535cde361e650565
