Fallback to current Feishu message for reactions

[zhulijin1991]

Summary

• Keep this PR focused on reaction message-id resolution only.
• Let react / reactions fall back to toolContext.currentMessageId when callers omit messageId / message_id.
• Remove the runtime emoji alias map from this branch so canonical Feishu reaction names are never silently rewritten.

Validation

• pnpm exec vitest run tests/reaction-defaults.test.ts
• pnpm run typecheck
• pnpm exec prettier --check src/messaging/outbound/actions.ts tests/reaction-defaults.test.ts
• git diff --check

Follow-up

Emoji-shape guidance should be handled separately in tool schema/description wording, without hidden runtime rewrites such as HEART -> LOVE or CLAP -> APPLAUSE.

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Restored from closed PR: #496