[Stuart B. Wilkins (stuwilkins)]

Zellij drops zero-width code points (emoji variation selectors, ZWJ) and has
no grapheme width mode (DEC 2027), so OpenTUI's default width counting drifts
from Zellij's grid. OpenTUI only redraws cells it thinks changed, so the
OpenCode TUI is left garbled until a resize. OpenTUI switches to wcwidth
counting for tmux and screen, but not for Zellij.

• Pass ZELLIJ, ZELLIJ_SESSION_NAME and ZELLIJ_PANE_ID into the sandbox, so
  OpenTUI can tell it runs inside Zellij (no Zellij socket is mounted).
• Set OPENTUI_FORCE_WCWIDTH=1 when ZELLIJ is set, unless the user already
  set OPENTUI_FORCE_WCWIDTH.
• Applies to bwopencode and bwopencode2 (shared build_env_vars).

Checked with --dry-run (the variables appear only when ZELLIJ is set) and
pre-commit (shfmt, shellcheck, codespell, gitleaks). Confirmed inside a
Zellij pane after restarting bwopencode2.

Assisted-by: opencode:claude-sonnet-5-5

[Copilot]

🟢 Approval recommended

The narrow shared-environment change preserves user overrides, serves both wrappers, and has no identified blocking issues.

No open issues 🎉

What changed in this PR

This PR addresses OpenCode TUI rendering drift inside Zellij by adjusting width-counting settings in the shared sandbox environment builder used by both wrappers.

Changes:

• Pass through Zellij session identifiers and default OPENTUI_FORCE_WCWIDTH to 1 inside Zellij, preserving explicit user values.
• Document the environment behavior in both OpenCode wrappers.

File	Description
lib/​bwrap_sandbox_lib.sh	Adds Zellij environment passthrough and the conditional width-counting default.
bin/​bwopencode2	Documents Zellij passthrough and width-counting behavior in comments.
bin/​bwopencode	Documents the same behavior in comments.

_{Review effort: Balanced}