Keep usernames literal in system messages

[MirrorCubeSquare]

Usernames containing card names can be parsed as card links or translated card text in system messages. For example, MirrorCubeSquare can have its Mirror prefix replaced in spectator notifications or repeated names in side-swap messages. Icon and special-message tokens inside a username can also be interpreted as formatting.

Keep usernames separate from renderable text using structured system-message parts. Only message text goes through card, icon, special-code, and pronoun processing. Apply this to lobby events, side swaps, commands, game notifications, and saved game logs. Retain the flattened :text field and the existing rendering fallback for older messages and replays.

Preserve player highlighting and timestamps, including after a player leaves. Explicitly mark spectator names before removing them from the lobby so their join/leave messages remain plain and have no player timestamp.

Validation on current master (d94d18cdc):

• Backend: game.core.say-test, web.lobby-test, and web.game-test — 13 tests, 279 assertions, no failures or errors.
• Browser: nr.utils-test — 5 tests, 117 assertions, all passing in Chromium. Covers translated card names, icon/special tokens, HTML escaping, timestamps, spectator styling, departed players, and legacy messages.
• Shadow CLJS release of :app — successful, zero compiler warnings.
• git diff --check — clean.

[MirrorCubeSquare]

This is a bugfix for issue #8862
After fix it shoud be like the following screen shot (this is taken from my testbench server)
under current version
MirrorCubeSquare will be rendered as"镜子CubeSquare"
and F2PDrafter will be rendered as "免付费内容建筑师"

[NoahTheDuke]

this is a great idea and i've considered something similar for a while (like card names or symbols). i'm gonna wait to review/merge this until i've merged my i18n message PR, because these both touch a lot of the same code paths.