feat(omo-codex): add start-work continuation component

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

packages/omo-codex/plugin/components/start-work-continuation/test/boulder-reader.test.ts

@@ -0,0 +1,63 @@
+import { describe, expect, it } from "vitest";
+
+import { parsePlanChecklist } from "../src/boulder-reader.js";
+
+describe("start-work plan checklist parser", () => {
+	it("#given top-level completed and incomplete checkboxes #when parsed #then counts remaining and total", () => {
+		// given
+		const markdown = ["# Plan", "", "## TODOs", "- [ ] First", "- [x] Done", "- [X] Also done", "- [ ] Second"].join(
+			"\n",
+		);
+
+		// when
+		const checklist = parsePlanChecklist(markdown);
+
+		// then
+		expect(checklist).toEqual({ remaining: 2, total: 4, nextTaskLabel: "First" });
+	});
+
+	it("#given nested checkboxes #when parsed #then ignores non-column-zero items", () => {
+		// given
+		const markdown = ["## TODOs", "- [ ] Top-level", "  - [ ] Nested", "\t- [ ] Tab nested", "- [x] Complete"].join(
+			"\n",
+		);
+
+		// when
+		const checklist = parsePlanChecklist(markdown);
+
+		// then
+		expect(checklist).toEqual({ remaining: 1, total: 2, nextTaskLabel: "Top-level" });
+	});
+
+	it("#given checkboxes outside counted sections #when parsed #then ignores unrelated top-level tasks", () => {
+		// given
+		const markdown = [
+			"# Plan",
+			"- [ ] Preamble task",
+			"## TODOs",
+			"- [ ] Build hook",
+			"## Acceptance Criteria",
+			"- [ ] Acceptance item",
+			"## Final Verification Wave",
+			"- [x] Run tests",
+			"- [ ] Run smoke",
+		].join("\n");
+
+		// when
+		const checklist = parsePlanChecklist(markdown);
+
+		// then
+		expect(checklist).toEqual({ remaining: 2, total: 3, nextTaskLabel: "Build hook" });
+	});
+
+	it("#given all top-level tasks complete #when parsed #then next task is null", () => {
+		// given
+		const markdown = ["## TODOs", "- [x] First", "- [X] Second"].join("\n");
+
+		// when
+		const checklist = parsePlanChecklist(markdown);
+
+		// then
+		expect(checklist).toEqual({ remaining: 0, total: 2, nextTaskLabel: null });
+	});
+});