Add history and notes tools for token-budget sessions (#39827)

## Why

Token-budget sessions need a way to recover prior conversation context and preserve working state across context-window transitions.

## What changed

- Add direct-model `history` tools for listing windows and items, reading items, and searching conversation contents.
- Add direct-model `notes` tools for listing, reading, searching, appending, and writing persistent notes.
- Route tool calls through the configured Codex backend with trusted session and agent context, bounded request arguments, and truncation-aware output handling.
- Expose the extension when `features.token_budget.use_history_notes_history` is enabled with an OpenAI provider and Codex backend authentication.

## Testing

- Cover tool registration, configuration changes, provider and authentication requirements, backend request context, encrypted output preservation, and request and response limits.

GitOrigin-RevId: 43b259f01014ba3f30803dd7cd5634942407a9bb

codex-rs/app-server/Cargo.toml

@@ -54,6 +54,7 @@ codex-guardian-v2 = { workspace = true }
 codex-git-utils = { workspace = true }
 codex-file-watcher = { workspace = true }
 codex-hooks = { workspace = true }
+codex-history-notes-extension = { workspace = true }
 codex-http-client = { workspace = true }
 codex-otel = { workspace = true }
 codex-plugin = { workspace = true }