[codex-analytics] emit goal lifecycle analytics (#27078)

## Why
- Currently, there is no analytics event for `/goal` behavior
- Existing events cannot identify goal execution or its resulting
outcome
- The original update in
[#26182](https://github.com/openai/codex/pull/26182) was implemented
before `/goal` moved into `codex-goal-extension`.

## What Changed
- Adds `codex_goal_event` serialization and enrichment to
`codex-analytics`
- Emits goal events from the canonical `codex-goal-extension` mutation
and accounting paths:
  - `created` when a new logical goal is persisted
  - `usage_accounted` when cumulative goal usage is persisted
  - `status_changed` when the stored goal status changes
  - `cleared` when the goal is deleted
- Preserves causal `turn_id` for turn driven events and uses null
attribution for external or idle lifecycle events
- Changes goal deletion to return the deleted row so `cleared` retains
the stable goal ID

## Event Details

Includes standard analytics metadata along with goal specific fields:
- `goal_id`: Stable ID stored in the local SQLite goal row and shared
across the goal's events
- `event_kind`: Observed operation (see the 4 lifecycle events cited in
the above bullet)
- `goal_status`: Resulting or last stored status: `active`, `paused`,
`blocked`, `usage_limited`, etc.
  - `has_token_budget`: Indicates whether a token budget is configured
  - `turn_id`: Causal turn ID, or null when no causal turn exists
- `cumulative_tokens_accounted`: Cumulative tokens on `usage_accounted`
events; null otherwise
- `cumulative_time_accounted_seconds`: Cumulative active time on
`usage_accounted` events; null otherwise

## Validation
- `just test -p codex-analytics -p codex-state -p codex-goal-extension`
- `just test -p codex-core -E 'test(/goal/)'`
- `just test -p codex-app-server`
- `cargo build -p codex-analytics -p codex-core -p codex-state -p
codex-app-server`

codex-rs/app-server/src/message_processor.rs

@@ -327,6 +327,7 @@ impl MessageProcessor {
                     app_server_extension_event_sink(outgoing.clone(), thread_state_manager.clone()),
                     auth_manager.clone(),
                     state_db.clone(),
+                    analytics_events_client.clone(),
                     thread_manager.clone(),
                     Arc::clone(&goal_service),
                     Arc::clone(&executor_skill_provider),