SEED-0093 P1 fixture origin

EVALUATION_ONLY. Planted fixtures with verdicts known in advance. Loopback only.

• /f1-edge-block - edge block: agent UA 403, browser UA 200
• /f2-challenge - challenge: agent UA challenge-shaped, browser UA 200
• /f3-js-only - client-side rendered, plus invalid JSON-LD
• /f4-no-conditional - no ETag, no Last-Modified, no 304
• /robots.txt - permits all, deliberately