fix(commit): created commits before agent teardown

- Ran commit host completion before commit-agent session disposal so mnemopi/autolearn teardown cannot preempt a valid proposal.

- Converted missing commit-agent host outputs and split-plan gaps into thrown errors so omp commit cannot resolve into exit 0 without creating a commit.

- Preserved caller GPG_TTY state instead of forcing a bogus signing TTY in git and non-interactive subprocess environments.

Fixes #4794

packages/coding-agent/src/utils/git.ts

@@ -197,7 +197,6 @@ const GIT_NON_INTERACTIVE_ENV = {
 	GIT_ASKPASS: "true",
 	GIT_EDITOR: "true",
 	GIT_TERMINAL_PROMPT: "0",
-	GPG_TTY: "not a tty",
 	SSH_ASKPASS: "/usr/bin/false",
 } satisfies Record<string, string>;
 const GH_NON_INTERACTIVE_ENV = {