Route internal visual comparisons through the direct WordPress origin

[chubes4]

Problem

After #2102 separated the direct WordPress Playground origin from the serialized exposed-preview proxy, authenticated editor commands correctly use server.wordpressUrl, but wordpress.visual-compare still resolves local URLs from server.serverUrl.

A real eight-route SSI university run proves the proxy is not a valid internal browser origin for canonical WordPress front-end routes:

• proxy origin: http://127.0.0.1:60757
• direct WordPress origin: http://127.0.0.1:53158
• staged source capture on the proxy succeeds
• candidate /, /contact/, /courses/, /events/, /faculty/, /news/, and /programs/ fail with ERR_TOO_MANY_REDIRECTS
• /research/ times out during the same canonical redirect loop
• editor commands using the direct origin validate 269/269 blocks

Root cause

browser-visual-compare.ts calls browserPreviewRouting(args, runtimeSpec, server.serverUrl) while editor commands use server.wordpressUrl ?? server.serverUrl. Internal source/candidate capture should remain same-origin with WordPress and avoid the serialized exposed-preview proxy. Public/exposed preview behavior remains a separate explicit mode.

Acceptance criteria

• Local wordpress.visual-compare uses the direct WordPress origin when available.
• Explicit public/routed preview modes retain their existing behavior.
• Add a real or contract-level regression proving local source and candidate routes do not traverse the preview proxy.
• Rerun all eight 27-university-department visual comparisons.

Related: #2095 and #2102.

AI assistance

• Model: OpenAI GPT-5.6 Sol
• Tool: OpenCode
• Used for: cross-stack reproduction and origin-routing diagnosis with Chris Huber.