fix: align visual pr and proof workflows

[sunwrobert]

Align create-pr and ship-with-proof with the updated personal workflow: publish a complete inline visual explanation, embed diagram PNGs when rendering and hosting are available, and keep browser verification optional.

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 compose inline visual explanation
 create HTML explainer
- require diagram PNG hosting and browser verification
+ embed diagram PNGs when rendering and supported hosting are available
+ otherwise publish the inline body and report the limitation
+ prefer API/CLI; do not launch a browser solely for diagram verification
 retain tests, end-to-end proof, thermo review, CI, and approvals

ship-with-proof still prohibits committing generated evidence and still treats missing actual recording/backend proof as a blocked gate. Only explainer-image delivery is optional.

Validation: skill validator, lint/format, and typecheck passed. The unit-test command passed with no tests present. Both updated skills match their personal copies. No generated artifacts or browser verification were needed for this instruction-file change.