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/test/commit-agentic-attribution.test.ts

@@ -46,4 +46,50 @@ describe("commit agent prompt attribution", () => {
 			expect(prompt.options?.expandPromptTemplates).toBe(false);
 		}
 	});
+
+	it("runs completion before session disposal", async () => {
+		const events: string[] = [];
+		const session = {
+			prompt: async () => {},
+			subscribe: () => () => {},
+			dispose: async () => {
+				events.push("dispose");
+			},
+		};
+
+		vi.spyOn(sdkModule, "createAgentSession").mockResolvedValue({ session } as unknown as CreateAgentSessionResult);
+		vi.spyOn(toolsModule, "createCommitTools").mockImplementation(options => {
+			options.state.proposal = {
+				analysis: {
+					type: "fix",
+					scope: "commit",
+					details: [],
+					issueRefs: [],
+				},
+				summary: "create commit before teardown",
+				warnings: [],
+			};
+			return [];
+		});
+
+		const model = getBundledModel("anthropic", "claude-sonnet-4-5");
+		if (!model) {
+			throw new Error("Expected claude-sonnet-4-5 model to exist");
+		}
+
+		await runCommitAgentSession({
+			cwd: "/tmp",
+			model,
+			settings: Settings.isolated(),
+			modelRegistry: {} as never,
+			authStorage: {} as never,
+			changelogTargets: [],
+			requireChangelog: false,
+			onComplete: state => {
+				events.push(state.proposal?.summary ?? "missing proposal");
+			},
+		});
+
+		expect(events).toEqual(["create commit before teardown", "dispose"]);
+	});
 });