fix: serialize type_schema as JSON in attestation type table output

[jbpros]

The server now returns type_schema as a JSON object instead of a Python repr string. The CLI was printing it with fmt %s, producing Go's map representation. Marshal it back to JSON for proper display.

[claude]

Claude finished @jbpros's task in 1m 36s —— View job

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PR Review: serialize type_schema as JSON in attestation type table output

• Run static analysis checks (go build, go vet, go mod tidy)
• Review code changes
• Post review feedback

Static Analysis

All checks pass:

• go build ./... — clean
• go vet ./... — clean
• go mod tidy — no changes to go.mod/go.sum

Review

This is a clean, well-scoped fix. The change correctly handles the server-side switch from Python repr strings to JSON objects by marshaling the type_schema value back to JSON before display.

What looks good:

• Proper error handling on json.Marshal with early return, consistent with the existing pattern in the function (e.g., line 162)
• Golden files updated to reflect the new JSON output (keys alphabetically sorted by json.Marshal, true instead of Python's True)
• Minimal diff — only touches what's necessary

One minor observation:

The json.Marshal output is compact (no indentation). For a potentially nested schema, this could be hard to read in table output. That said, this matches the existing behavior of other fields and keeps the table layout clean, so it's a reasonable choice for now. Pretty-printing could be a follow-up if users find it hard to read.

No issues found. LGTM — this is ready to merge.