tui: @ directory completion yields double slash; /cd select never submits exact path

Summary

Two related directory-completion problems in the TUI prompt: (1) the @ file reference autocomplete produces a double slash (@dir//) when expanding a directory, breaking further drill-down; (2) in /cd directory argument completion, prompt.autocomplete.select only re-inserts the already-exact path and closes the popup without submitting, leaving the command unexecuted.

Environment

• opencode version: 2.0.8
• OS: Darwin 27.2.0 (darwin arm64)
• Terminal: TERM_PROGRAM=WezTerm, TERM=xterm-256color, COLORTERM=truecolor
• Shell: /bin/zsh
• Install/channel: latest
• Active plugins: @prevalentware/opencode-goal-plugin, billion-context@0.1.118-pr.936.774

Reproduction

Both reproduced in a real terminal (tmux-captured pty) with the TUI running v2.0.8.

Bug 1: @ directory expansion yields @dir//

1. In a project containing a directory sub1/, type @sub1 in the prompt.
2. Select the directory entry and press the prompt.autocomplete.complete key (Enter in my keymap; Tab by default).
3. The input becomes @sub1// and the popup switches to "No matching files" — drill-down into the directory is broken.

Root cause (v2.0.8 source): packages/tui/src/component/prompt/autocomplete.tsx, expandDirectory() — the @ branch runs input.insertText("@" + selectedPath + "/") unconditionally, while the server fs.find already returns directory paths with a trailing slash (sub1/). The adjacent directory-mode branch (/cd, same function) guards with selectedPath.endsWith(path.sep) ? selectedPath : selectedPath + path.sep; the @ branch lacks this guard. Git history: at commit 106f8e94 the line was insertText("@" + path) (correct, since dir paths carry a trailing slash); a later commit added the extra + "/".

Bug 2: /cd select never submits, even on an exact path

Keymap: prompt.autocomplete.complete: return, prompt.autocomplete.select: shift+return.

1. Type a complete, valid directory argument: /cd ~/.config/opencode/scripts/
2. The popup shows that exact directory as the first (exact-match) entry plus its children.
3. Press prompt.autocomplete.select (Shift+Enter). The popup closes and nothing happens — the working directory is unchanged; the text just sits in the input.
4. Only a second Enter (with the popup now hidden) submits the command.

Root cause: in the same file, select()'s directory branch only calls selected.onSelect?.() (which is insertDirectory(value)) and hide(true) — there is no submission path. When the typed argument is already an exact, valid directory, select re-inserts identical text and does nothing, which reads as "the key didn't work".

A related UX papercut that compounds this: the /cd popup lists only the current directory itself and its children — no parent or sibling entries — so after drilling down, pressing complete on the first (exact/self) entry is a no-op and the picker appears "stuck". To reach a sibling directory the user must know to type ...

Expected Behavior

1. @ directory expansion should not duplicate the trailing slash: @sub1/ and drill-down should continue to work.
2. When the /cd argument is already an exact valid directory, select should submit the command (or an explicit binding should exist that does), rather than re-inserting identical text.

Actual Behavior

1. @sub1// — double slash, autocomplete breaks.
2. Working directory unchanged after select; a second Enter with the popup dismissed is required.

Additional Context

• Reproducibility: both 100% consistent.
• Bug 1 was verified against the v2.0.8 tagged source and via git history (correct at 106f8e94, broken after a later change to expandDirectory).
• Bug 2 verified by pty reproduction: after Shift+Enter the status-bar cwd is unchanged; after a following Enter it switches.
• Suggested fix for bug 1: apply the same endsWith(path.sep) guard in the @ branch of expandDirectory().
• Suggested fix for bug 2: in select()'s directory branch, submit when the option is the exact match for the current query (or document/select a "submit" affordance for argument popups).

Start in packages/tui/src/component/prompt/autocomplete.tsx and read expandDirectory() and select() for the @ and /cd directory branches. Reproduce both flows in the TUI, then verify that directory expansion preserves one trailing slash and that selecting an exact /cd directory submits the command instead of only reinserting the path.