test(qa): align AI oracles with fixtures and honor QA_OUT_DIR (#686)

The ocr oracle demanded six pangram words when ocr-clean.png prints five; the ocr-pdf oracle expected a searchable PDF when the tool's contract is text extraction; media-30s.mp4 was eight seconds long. Fix all three, regenerate tool-contract.json from current schemas, record the new fixture in the manifest, and add a QA_OUT_DIR override so parallel machines stop clobbering each other's lane output. Fixes #677.

tests/qa/tool-contract.json

@@ -3374,7 +3374,7 @@
       },
       {
         "key": "sobelThreshold",
-        "values": [1, 10.5, 20, null]
+        "values": [1, 11, 20, null]
       },
       {
         "key": "square",