fix(tui): handle hidden app git directives

[fcoury-oai]

Why

The desktop App treats ::git-* directives as hidden control messages: it keeps them out of the visible transcript while still using them to react to successful git actions. When the TUI replays App-authored sessions today, it treats those directives as ordinary assistant markdown instead, which both leaks internal control text to the user and leaves the two clients with different handling for the same assistant output.

What changed

• Added TUI support for the App's existing git action directives.
• Hide those directives from live assistant output, consolidated stream history, copied / notification fallback text, replayed transcripts, and resume previews.
• Replayed directives are render-only: they are hidden from transcript surfaces but never trigger workspace probes or metadata updates.
• For live git-create-branch directives, re-read the actual workspace branch through the existing workspace-command path before syncing stored thread metadata, so local and remote sessions both use workspace state as the source of truth.

How to Test

1. Start a Codex session in the desktop App and complete a turn that emits a git directive such as ::git-push{...}.
2. Resume that session in the TUI.
3. Confirm the assistant response is shown without the raw ::git-* line.
4. Also inspect the resume picker preview for the same session and confirm the internal directive is omitted there too.
5. For a live git-create-branch directive, verify the stored thread branch follows the branch actually checked out in the workspace, without adding any visible transcript text.

Targeted tests:

• cargo test -p codex-tui git_action --no-fail-fast