Unify context snapshots and group requests into windows (#44932)

## What changed

- Use one renderer for captured requests, raw request bodies, and input items. Show only appended items when inputs extend the previous request and settings match; start a new snapshot window otherwise and explain the boundary.
- Add optional request settings and tool inventory deltas. Normalize volatile values with stable labels, preserve multiline content, and fingerprint omitted content so changes remain visible.
- Migrate existing context snapshots and expand compaction snapshots to include request history.

## Testing

Add focused tests for window boundaries, cache key changes, tool deltas, shared item rendering, stable normalization, and fingerprints. Assert that the follow-up request after pre-turn compaction includes the working directory override.

GitOrigin-RevId: 6445b014081208ea432b1f3e2ac835c5e4955cb0

codex-rs/core/src/session/snapshots/codex_core__codex_tests__fork_startup_context_then_first_turn_diff.snap

@@ -4,11 +4,16 @@ expression: snapshot
 ---
 Scenario: First request after fork when startup preserves the parent baseline, the fork changes approval policy, and the first forked turn enters plan mode.
 
-## First Forked Turn Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
-02:message/user:fork seed
+## Window 1
+-- request 1 (turn; First Forked Turn Request) --
+00:message/developer:
+    <PERMISSIONS_INSTRUCTIONS>
+01:message/user:
+    <ENVIRONMENT_CONTEXT:cwd=<CWD>>
+02:message/user:
+    fork seed
 03:message/developer[2]:
     [01] <PERMISSIONS_INSTRUCTIONS>
     [02] <collaboration_mode>Fork turn collaboration instructions.</collaboration_mode>
-04:message/user:after fork
+04:message/user:
+    after fork

codex-rs/core/src/session/tests.rs

@@ -179,7 +179,6 @@ use core_test_support::PathBufExt;
 use core_test_support::PathExt;
 use core_test_support::context_snapshot;
 use core_test_support::context_snapshot::ContextSnapshotOptions;
-use core_test_support::context_snapshot::ContextSnapshotRenderMode;
 use core_test_support::responses;
 use core_test_support::responses::ev_assistant_message;
 use core_test_support::responses::ev_completed;
@@ -3793,10 +3792,7 @@ async fn fork_startup_context_then_first_turn_diff_snapshot() -> anyhow::Result<
     let snapshot = context_snapshot::format_labeled_requests_snapshot(
         "First request after fork when startup preserves the parent baseline, the fork changes approval policy, and the first forked turn enters plan mode.",
         &[("First Forked Turn Request", &request)],
-        &ContextSnapshotOptions::default()
-            .render_mode(ContextSnapshotRenderMode::KindWithTextPrefix { max_chars: 96 })
-            .strip_capability_instructions()
-            .strip_agents_md_user_context(),
+        &ContextSnapshotOptions::default().rewrite_known_segments(),
     );
 
     let mut settings = insta::Settings::clone_current();