Improve CLI audits and developer experience

[ChristianPavilonis]

Goal

Track the CLI audit and developer-experience improvements identified while working on rc/202608.

The work covers audit previews and generated configuration, creative-opportunity discovery, redirect handling, general CLI output, adapter/tooling guidance, and dev-proxy diagnostics.

The question of whether ts audit generate <url> should crawl beyond the supplied page is intentionally deferred for later discussion. The minimum file-descriptor threshold for the dev proxy also remains open.

Sub-issues

• Preview generated audit output #1056 Preview generated audit output
• Omit redundant and placeholder values from generated config #1057 Omit redundant and placeholder values from generated config
• Accept apex and www redirects during audits #1058 Accept apex and www redirects during audits
• Preserve all creative opportunities during generation #1059 Preserve all creative opportunities during generation
• Improve general human-readable CLI output #1060 Improve general human-readable CLI output
• List supported adapters in ts build help #1061 List supported adapters in ts build help
• Improve missing vendor CLI errors and document prerequisites #1062 Improve missing vendor CLI errors and document prerequisites
• Show help for a bare ts dev proxy invocation #1063 Show help for a bare ts dev proxy invocation
• Check the dev-proxy file-descriptor limit #1064 Check the dev-proxy file-descriptor limit
• Decide whether ts audit generate should crawl beyond the supplied page #1065 Decide whether ts audit generate should crawl beyond the supplied page