Stale insta snapshots in tui_main::render_impl::tests (6 failing, branch name leaked)

[JDonaghy]

Problem

Once the binary-test build is unbroken (see sibling issue for `render.rs` test compile), 6 snapshot tests under `tui_main::render_impl::tests` fail:

• `snapshot_command_line`
• `snapshot_insert_mode`
• `snapshot_line_numbers`
• `snapshot_normal_mode`
• `snapshot_split_panes`
• `snapshot_visual_selection`

Status-bar diff (example, `snapshot_insert_mode`):

```

• INSERT  [No Name]  issue-385-appshell-side Ln 1, Col 1
  

• INSERT  [No Name]    󰘖 utf-8 LF Spaces: 4  Ln 1, Col 1
  

```

Two problems:

1. Stale: the status bar now renders file-info icons (utf-8, LF, indent) instead of the git branch. The committed snapshots predate that rendering change.
2. Environment-leaked: the OLD snapshot literally contains `issue-385-appshell-side` — whoever captured the snapshot ran `INSTA_UPDATE=1` on the `issue-385-appshell-side` branch and the git-branch portion of the status bar leaked into the fixture. Snapshots that depend on the current branch name will never pass cleanly in CI.

Fix sketch

• Run `cargo insta accept` on a clean develop branch (after the compile fix lands) and inspect the 6 diffs to confirm the new status-bar shape is intended.
• For env-leak: either stub out `git_branch` in the snapshot test setup, or change the test scaffolding to render with a fixed mock branch name. Otherwise the next person to run `INSTA_UPDATE` on a different branch re-introduces the same flake.

Surfaced by

PR #435 smoke gate (Session 382). Hidden until that PR's collateral test-compile fix exposed them.

Related

Sibling issue: render.rs test build broken — must land first.