Prompt primitives should not append duplicate punctuation

[JeffreyCA]

Problem

The core prompt primitives always append : to the supplied message. When a caller already ends its message with punctuation, the rendered prompt contains doubled punctuation such as ?: or ::.

This affects the shared Confirm, Prompt, Select, and MultiSelect renderers in cli/azd/pkg/ux/, so it should be fixed once in the primitive rather than worked around at individual call sites.

Examples from main

cli/azd/pkg/infra/provisioning/provision_validation.go passes a confirm message ending in a question mark:

Message: fmt.Sprintf("Proceed with %s despite the warnings above?", action),

The Confirm primitive appends another colon, producing output like:

? Proceed with provisioning despite the warnings above?: [Y/n]

cli/azd/pkg/infra/provisioning/bicep/bicep_provider.go passes a select message ending in a colon:

Message: "Select a deployment to continue:",

The Select primitive appends another colon, producing output like:

? Select a deployment to continue::

The current primitive behaviour comes from renderers formatting every message as %s: regardless of its final character.

Expected behaviour

Append : only when the trimmed message does not already end in terminal punctuation. Messages ending in punctuation such as ?, :, ., !, or ; should retain that punctuation and receive only the trailing space needed before the hint, value, or selected result.

Examples:

Input message	Rendered message segment
Continue	Continue:
Continue?	Continue?
Select a deployment:	Select a deployment:

Acceptance criteria

• Centralize the formatting rule in a small shared helper.
• Apply it consistently to Confirm, Prompt, Select, and MultiSelect.
• Preserve the existing colon for messages without terminal punctuation.
• Trim trailing whitespace before checking the final character.
• Add focused unit coverage for plain messages and messages ending in each supported punctuation character.
• Confirm existing prompt rendering and interaction tests continue to pass.