Artifact file_read results can now inline the file's full content

What

• When the Artifact tool's file_read result is rendered, if the read includes a content string it's now appended in full below the summary line, so the caller no longer necessarily needs to separately read the saved file.
• A note is shown when the content is a "reading copy" with reserved tag names neutralized.
• The underlying schema for served files gained content (capped in length) and content_scrubbed fields; elsewhere, content/content_scrubbed are stripped from file_read payloads before being logged.

Why Inlining the file content saves an extra round trip: Claude can see what it just read without issuing a follow-up read call, while the scrubbing step keeps sensitive content out of logs.