Unicode not displayed correctly in checkpoints served from Worker

[lukevalenta]

When serving static log data from the the Worker (instead of the R2 bucket), the unicode em dash (U+2014) character is not displayed correctly, probably since we're not specifying content-type.

$ curl -s https://static-ct.cloudflareresearch.com/logs/cftest2025h1a/checkpoint
static-ct.cloudflareresearch.com/logs/cftest2025h1a
207510
ophIa0bLvuQOHnH8uUuOp4tDCF0WarYd3y2B0O6edHA=

— grease.invalid LIllCfegApBERw8S69sSU4sBYhjx1CM3Bo6+sWzRZXPH/yayTACKI7TZAIfTMg1d71+O8tbMQMOnBCCID98GOP4+Az9CFMIa1VBKeqQU78qCXA==
— static-ct.cloudflareresearch.com/logs/cftest2025h1a pRYz5GvDifjUQo1ZfWDSjJDGiCzIXuk4l8P15uma+grPBSk8bgq7DRmj1hN7lYlPpKxm828=
— static-ct.cloudflareresearch.com/logs/cftest2025h1a iZLxVQAAAZYXJSLbBAMARzBFAiB4YZS3mfE4UIKEJ4aXxo/DnnPqlWtu79aJNNLrCyP62wIhAPNl6rJFtav330TfbWYm+ThDViyIYNtFIZg06t2yc9rU
— static-ct.cloudflareresearch.com/logs/cftest2025h1a gMMtNKMOZD8x0SOmoOAN7ui4d3YqYN5W/XDS9TC1hVgjSqpE3rWglETjq3IeIWuJbsZ6FR1tAlTim6DeEBGnRRKWbQI=

Versus retrieving the checkpoint from R2:

$ curl -s https://static-ct-public-cftest2025h1a.cloudflareresearch.com/checkpoint
static-ct.cloudflareresearch.com/logs/cftest2025h1a
207510
ophIa0bLvuQOHnH8uUuOp4tDCF0WarYd3y2B0O6edHA=

— static-ct.cloudflareresearch.com/logs/cftest2025h1a /Md0ap+2xUWz7dDFT/rrizKia9e/NTb5cmw1NxV+Mmh1SX6ShxvUYcu+m9Oa54InzgyP7YbV6SXw62l3XovqfMiOGUUrwW1hCSThnnFa8jxu/80d88DmdPgDJjPv
— grease.invalid UwWfcJ0eO01W7bfjqZ5o1PVs789Chj21K3l0FAHaitVyuBnkVHXAklO1zmRXCvYeOg0bhw==
— static-ct.cloudflareresearch.com/logs/cftest2025h1a iZLxVQAAAZYXI/3jBAMASDBGAiEAl2KsgvPcxEm4Q0nVBMNBVc16hvj+lIlT01VwpK/JSC8CIQDaQG+3sxqIkNY1AJptsis4aQFAlLLEfGH7SkDktl7yCA==
— static-ct.cloudflareresearch.com/logs/cftest2025h1a gMMtNKMOZD8x0SOmoOAN7ui4d3YqYN5W/XDS9TC1hVgjSqpE3rWglETjq3IeIWuJbsZ6FR1tAlTim6DeEBGnRRKWbQI=