Improve Ghostel terminal integration

[tninja]

This improves the Ghostel terminal backend integration so ai-code preserves Ghostel's own process behavior while still applying ai-code session lifecycle handling.

The change keeps Ghostel title tracking and buffer-on-exit behavior disabled after ghostel-exec, preserves and chains Ghostel's native process sentinel before ai-code cleanup, and routes Ghostel resize handling through Ghostel's own window-size adjustment path. It also treats newer Ghostel ghostel--input-mode copy state as terminal navigation mode while keeping the older ghostel--copy-mode-active path compatible.

The vterm and eat backends are not changed. I verified the backend dispatch paths with targeted vterm/eat tests and runtime probes, and added Ghostel regression coverage for resize handling, sentinel chaining, title tracking, and copy-mode detection.

Verification:

• emacs -Q -batch -L . --eval "(setq load-prefer-newer t)" -l ert -l test/test_ai-code-backends-infra.el -f ert-run-tests-batch-and-exit
• emacs -Q -batch -L . -l ert --eval "(mapc #'load-file (file-expand-wildcards \"test/test_*.el\"))" -f ert-run-tests-batch-and-exit
• emacs -Q -batch -L . --eval "(setq load-prefer-newer t)" -f batch-byte-compile ai-code-backends-infra.el ai-code-backends-infra-vterm.el ai-code-backends-infra-eat.el ai-code-backends-infra-ghostel.el
• git diff --check

[tninja]

@copilot resolve the merge conflicts in this pull request

[Copilot]

Pull request overview

This PR refines the Ghostel terminal backend integration so ai-code preserves Ghostel's native lifecycle (title tracking, kill-on-exit, sentinel) while still applying ai-code's session cleanup. It also routes resize handling through Ghostel's window-size adjuster and recognizes the newer ghostel--input-mode copy state.

Changes:

• Reapply --configure-ghostel-buffer after ghostel-exec so title tracking and kill-on-exit stay disabled, and capture Ghostel's native sentinel in a process property.
• In --finalize-started-session, chain any captured Ghostel sentinel before invoking ai-code cleanup.
• Use Ghostel's --window-adjust-process-window-size for sync, and treat ghostel--input-mode = 'copy as navigation mode.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
ai-code-backends-infra.el	Routes Ghostel resize through its native handler, chains a saved Ghostel sentinel before cleanup, plus docstring tweaks.
ai-code-backends-infra-ghostel.el	Reconfigures Ghostel buffer post-ghostel-exec, stashes native sentinel, adds ghostel--input-mode copy detection, disables ghostel-kill-buffer-on-exit.
test/test_ai-code-backends-infra.el	Adds regression coverage for resize routing, sentinel chaining/preservation, title tracking, and new copy-mode detection.

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved the merge conflicts by merging origin/main into this branch and reconciling ai-code-backends-infra.el so both the latest vterm resize/flush behavior and Ghostel-specific handling are preserved. Addressed in commit 84cff89.

[chatgpt-codex-connector]

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