fix(desktop): localize the group-activity feed's row verbs

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Summary

PR #113430 localized the bot-roster menu and group-row chrome, but its own comment disclosed one remaining gap: group-activity.ts::GROUP_ACTIVITY_LABELS was still a hardcoded English Record<GroupActivityKind, string>, so the room's Activity feed rows ("Alice sent a message", "Bob is working…", etc.) never followed the active locale.

Changes

• Added 12 new group.* keys to the BotsMessages interface and all four locale bundles (en/ja/zh/zh-hant):
  • 9 speaker-taking verbs (activityQueued, activityWorking, activityReplied, activityPassed, activityTimedOut, activityFailed, activityDelivered, activityHeld, activityStopped) as (who: string) => string functions — matching the established memberThinking/b.bot.unpinnedToast(...)-style precedent (a function embeds the name so a locale can place the particle/word order right after it, e.g. Japanese ${who}が…), not raw string concatenation.
  • 3 standalone strings (activityCancelled, activitySettled, activityCapped) for the room-level lines that never take a speaker.
• Rewrote groupActivityLabel() to read these via botsText() instead of the local hardcoded map.
• Also routed the "You" display side through the already-existing g.you translated string (the event.member === 'You' sentinel comparison itself is unrelated backend data and stays as-is).

Test plan

• Extended i18n.test.ts's existing generic locale-coverage tests with a new case: every speaker-taking verb keeps the sentinel argument in its output, and every locale's activity strings differ from English's.
• Mutation-verify: reverted the two production files, confirmed the new test fails (TypeError: fn is not a function, since the pre-fix bundle has no activityQueued etc.); restored the fix, all tests pass again.
• group-activity.test.ts's existing 'labels read like a person wrote them...' test (asserting exact English strings like 'You sent a message') still passes unchanged — confirms the English output is byte-identical to before.
• tsc --noEmit and eslint clean on all three touched files.

Note: group-activity.test.ts > epoch scoping > queues follow-ups without cancelling the active turn or losing its reply delta fails both with and without this change (confirmed by stashing all changes and rerunning against a clean baseline) — a pre-existing, timing-sensitive flake unrelated to this PR.

🤖 Generated with Claude Code

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This was generated by AI during triage.

Related follow-up to merged #113430: that change localized roster and group-row chrome, while this PR covers the remaining hard-coded group-activity feed verbs.