Separate local and remote plugin analytics IDs (#29495)

## Why

Plugin analytics overloaded `plugin_id`: most events used the Codex
`<plugin>@<marketplace>` identity, while remote install events used the
backend plugin ID. That makes the same field change meaning across event
types and complicates downstream identity resolution.

This change makes the contract unambiguous:

- `plugin_id`: the local Codex `<plugin>@<marketplace>` identity, when
resolved
- `remote_plugin_id`: the backend plugin identity, when available

For a remote install failure that happens before plugin details resolve,
`plugin_id` is `null` and `remote_plugin_id` remains populated.

## What changed

All six plugin analytics events use the same identity contract:

- `codex_plugin_installed`
- `codex_plugin_install_failed`
- `codex_plugin_uninstalled`
- `codex_plugin_enabled`
- `codex_plugin_disabled`
- `codex_plugin_used`

Remote identity is resolved from the current installed-plugin snapshot
first, with persisted install metadata as fallback. The telemetry
metadata type keeps local identity optional for failures that occur
before remote details are available.

The app-server test client's manual analytics smokes now find remote
mutation events through `remote_plugin_id` and validate that `plugin_id`
remains local.

## Remote uninstall

Resolve and capture telemetry metadata before removing the local plugin
cache, then emit `codex_plugin_uninstalled` after the backend confirms
success. The event is also emitted when backend uninstall succeeds but
local cache cleanup reports `CacheRemove`.

If a concurrent remote-cache refresh removes the local bundle before
telemetry capture, the already-fetched remote plugin detail supplies
fallback capability metadata.

## Validation

- `just test -p codex-analytics` — 82 passed
- `just test -p codex-core-plugins` — 271 passed
- `just test -p codex-app-server-test-client` — 5 passed
- `just test -p codex-plugin` — 3 passed
- `just test -p codex-app-server plugin_install` — 37 passed
- `just test -p codex-app-server plugin_uninstall` — 10 passed

The production app-server install/uninstall flow was also exercised
against `plugins~Plugin_f1b845ac33888191ac156169c58733c2`
(`build-ios-apps@openai-curated-remote`), and the plugin's original
uninstalled state was restored.

codex-rs/plugin/src/lib.rs

@@ -70,9 +70,10 @@ pub struct PluginHookSource {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct PluginTelemetryMetadata {
-    pub plugin_id: PluginId,
-    /// Optional backend identifier for remote plugins, used when analytics
-    /// should report the remote id instead of the local plugin cache id.
+    /// Local plugin identifier used by Codex configuration and the plugin cache,
+    /// when it has been resolved.
+    pub plugin_id: Option<PluginId>,
+    /// Optional backend identifier for remote plugins.
     pub remote_plugin_id: Option<String>,
     pub capability_summary: Option<PluginCapabilitySummary>,
 }