Extract ChatMessageContent from PureReportActionItem

[cristipaval]

Extract the default chat message branch (the big else at the end) from PureReportActionItem into a standalone ChatMessageContent component. This is the most impactful extraction — it moves 3 useOnyx calls, 2 custom hooks, the actionableItemButtons useMemo, moderation state, and 2 context provider useMemos so they only run for actual chat messages.

PR: #88112

Issue Owner

Current Issue Owner: @LukasMod

[LukasMod]

Per-item savings: -10 Onyx subscriptions per visible ADD_COMMENT action item.

Measured scaling (identical content, baseline vs Phase 4):

• 38 items → -380 subs (10/item)
• 86 items → -860 subs (10/item)

What moved:

• nvp_private_amountOwed, nvp_private_billingGracePeriodEnd, sharedNVP_private_billingGracePeriodEnd_ now only subscribed inside ChatActionableButtons (behind mayHaveActionableButtons guard, mounts rarely)
• useActivePolicy (2 internal subs), usePreferredPolicy (3 internal subs), trackExpenseTransaction, draftTransactionIDs same treatment

Cost: +1 fiber node per chat message (the ChatMessageContent wrapper).

Before	After

[LukasMod]

PR ready for review #88112

[cristipaval]

that is great! thanks @LukasMod 🙏