fix: prevent DCS passthrough race in tdl causing nvim E349 on startup

[peregrinus879]

Summary

When tdl launches OpenCode (alias c) alongside nvim, OpenCode's TUI framework sends DCS passthrough terminal capability queries during initialization (wrapped as \ePtmux;\e...\eST). Because tdl creates the AI pane last, that pane has focus when send-keys fires. The queries are forwarded to the terminal emulator via allow-passthrough=on in tmux.conf.

The subsequent select-pane shifts focus to the editor pane before the terminal's responses arrive. Tmux delivers the incoming responses to the now-focused editor pane, where nvim misinterprets the leaked bytes as normal-mode commands, triggering E349 ("No identifier under cursor") as a one-time flash on startup.

Why this only affects OpenCode, not Claude Code

• OpenCode (alias c / opencode): Its TUI framework sends DCS passthrough terminal capability queries (DECRQM, XTVERSION, Kitty graphics queries, pixel resolution queries, etc.) immediately during startup. These are the sequences that get misrouted.
• Claude Code (alias cx / claude): Does not send DCS passthrough queries during TUI initialization. The cx alias also includes a printf screen-clear before launching, which produces only CSI sequences handled internally by tmux and generates no passthrough traffic.

Fix

Temporarily disable allow-passthrough on AI panes at creation time using per-pane tmux set-option -p, blocking the DCS queries during the race window. After the focus transition completes, a background subshell restores passthrough after 1 second, once the AI tool's TUI init is finished. This preserves full passthrough capability for AI panes during normal use.

Reproduction

1. tmux with allow-passthrough=on and focus-events=on (Omarchy defaults)
2. tdl c (OpenCode in AI pane, nvim in editor pane)
3. E349 flashes in nvim on startup

Confirmed not affected

• tdl cx (Claude Code)
• nvim alone
• Any tdl invocation without OpenCode

Test plan

• Run tdl c repeatedly; E349 should never appear
• Run tdl cx; confirm no regression
• Run tdl c cx (dual AI); confirm no regression
• Confirm passthrough still works on AI panes after the 1-second restore (e.g., any tool needing DCS passthrough)
• Test over SSH to confirm fix holds with network latency

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR fixes a race condition where OpenCode's DCS passthrough terminal capability queries during TUI initialization are misrouted to the editor pane, causing nvim to display E349 ("No identifier under cursor") on startup.

Changes:

• Disable allow-passthrough on AI panes immediately after creation to block DCS queries during the race window
• Disable allow-passthrough on secondary AI pane if present
• Re-enable allow-passthrough on AI panes after 1 second via background subshell, once OpenCode's TUI initialization completes

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