Add public memory link to TUI details

[humandebri]

Summary

• add an Open public memory action to the Memories detail pane when anonymous has reader access
• open https://memory.kinic.xyz/m/{canister_id} through the existing external browser effect
• document the TUI action and cover anonymous/2vxsx-fae reader cases

Tests

• cargo test -p kinic-cli public_action
• cargo test -p kinic-cli public_memory_url
• .local/check.sh