feat(packages/coding-agent): added terminal protocol debug diagnostics

- Added debug menu options for terminal state and protocol checks with new handlers.
- Added terminal diagnostics models and collectors to report geometry, protocol flags, and multiplexer data.
- Added protocol-probe utilities to encode RGB PNGs, generate sample content, and render test panels.
- Added support components for verbatim line rendering and OSC66-scaled text rows.
- Added tests validating image encoding, OSC66 output, and terminal state formatting.

packages/coding-agent/test/debug/protocol-probe.test.ts

@@ -0,0 +1,44 @@
+import { beforeAll, describe, expect, it } from "bun:test";
+import { getImageDimensions } from "@oh-my-pi/pi-tui";
+import { buildLargeTextLines, buildSampleImage, encodeRgbPng } from "../../src/debug/protocol-probe";
+import { initTheme } from "../../src/modes/theme/theme";
+
+beforeAll(async () => {
+	// buildLargeTextLines styles the OSC 66 span through the global theme singleton.
+	await initTheme();
+});
+
+describe("encodeRgbPng / buildSampleImage", () => {
+	it("emits a PNG whose IHDR dimensions decode back to the requested size", () => {
+		// The graphics test relies on producing a *valid* PNG: Kitty/iTerm2 hand
+		// the bytes to the terminal and Sixel decodes them natively, so a malformed
+		// header (wrong CRC, bad chunk framing) silently breaks the whole panel.
+		const sample = buildSampleImage(48, 24);
+		expect(sample.mimeType).toBe("image/png");
+		expect(sample.dimensions).toEqual({ widthPx: 48, heightPx: 24 });
+
+		const decoded = getImageDimensions(sample.base64, "image/png");
+		expect(decoded).toEqual({ widthPx: 48, heightPx: 24 });
+	});
+
+	it("begins with the PNG signature and round-trips arbitrary pixel sizes", () => {
+		const png = encodeRgbPng(3, 2, new Uint8Array(3 * 2 * 3));
+		expect(Array.from(png.subarray(0, 8))).toEqual([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
+
+		const decoded = getImageDimensions(Buffer.from(png).toString("base64"), "image/png");
+		expect(decoded).toEqual({ widthPx: 3, heightPx: 2 });
+	});
+});
+
+describe("buildLargeTextLines", () => {
+	it("encodes each scale as an OSC 66 span and reserves scale-1 blank rows below it", () => {
+		const lines = buildLargeTextLines([2, 3]);
+		// scale 2 → 1 reserved row, scale 3 → 2 reserved rows.
+		expect(lines).toHaveLength(5);
+		expect(lines[0]).toContain("\x1b]66;s=2;");
+		expect(lines[1]).toBe("");
+		expect(lines[2]).toContain("\x1b]66;s=3;");
+		expect(lines[3]).toBe("");
+		expect(lines[4]).toBe("");
+	});
+});