[Fix] Memory page links render as blocked text

[roomote-roomote]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Render canonical Memory page references such as people/... as in-app links instead of Streamdown's [blocked] placeholder.
• Route those links through the same query-parameter selection used by the Memory browser while preserving existing URL parameters.
• Keep arbitrary relative paths and unsafe URL protocols non-interactive, and add focused regression coverage for both allowed and blocked destinations.

Why this change was made

Task memories now include canonical person references, but their relative Markdown destinations were rejected by the preview's URL hardener. The stored relationship was correct while the visible initiator line appeared broken and could not open the referenced person page.

Impact

Admins can navigate from a memory's linked references to the corresponding page inside the existing Memory browser. The allowlist is limited to registered Memory namespaces and does not broaden access or bypass the existing admin-scoped page lookup.

Screenshots

Representative Memory data was rendered on the real local product surface because the sandbox has no configured Memory service URL. This demonstrates the UI treatment; automated coverage verifies selection behavior and unsafe-link rejection.

[roomote-community]

No code issues found. See task

_{Reviewed 3aca95a}