fix: load storage state at launch when --state / AGENT_BROWSER_STATE is set (#1241)

* fix: load storage state at launch when --state / AGENT_BROWSER_STATE is set

The `--state` flag and `AGENT_BROWSER_STATE` env var were documented as
restoring saved browser state (cookies + localStorage) at launch, but
`load_state()` was never called after the browser started. The feature
has been broken since it was introduced.

Adds `try_load_storage_state()` and calls it from every early-return
path in `auto_launch()` (lazy launch triggered by commands like
`navigate`) and from `handle_launch()` (explicit `launch` command).

Also adds 4 e2e tests covering all state-persistence paths:
- Explicit launch with `storageState` field
- Auto-launch via `AGENT_BROWSER_STATE` env var
- Session-name auto-restore via `try_auto_restore_state`
- Explicit `state_load` command (baseline sanity check)

Fixes #1164.

* style: apply cargo fmt to e2e_tests.rs

Reformats a single long format\! call to satisfy CI's rustfmt check.
No behavior change.

* fix: call try_load_storage_state in all handle_launch branches

The CDP URL, CDP port, auto-connect, and provider early-return branches
were skipping storage state loading because try_load_storage_state was
only called in the normal BrowserManager::launch() path at the bottom
of handle_launch().

Also compute storage_state_owned once and reuse it across all branches
rather than borrowing storage_state (a &str tied to cmd) in a helper
that needs an owned Option<String>.

* Fix storage state reload on reused launches

* Fix storage-state launch errors

* Fix storage state replay ordering

* Align storage-state errors across launch paths

* Fix storageState launch cleanup