refactor: apply minimal tfcode branding

- Rename packages/opencode → packages/tfcode (directory only)
- Rename bin/opencode → bin/tfcode (CLI binary)
- Rename .opencode → .tfcode (config directory)
- Update package.json name and bin field
- Update config directory path references (.tfcode)
- Keep internal code references as 'opencode' for easy upstream sync
- Keep @opencode-ai/* workspace package names

This minimal branding approach allows clean merges from upstream
opencode repository while providing tfcode branding for users.

packages/tfcode/test/cli/github-action.test.ts

@@ -0,0 +1,198 @@
+import { test, expect, describe } from "bun:test"
+import { extractResponseText, formatPromptTooLargeError } from "../../src/cli/cmd/github"
+import type { MessageV2 } from "../../src/session/message-v2"
+import { SessionID, MessageID, PartID } from "../../src/session/schema"
+
+// Helper to create minimal valid parts
+function createTextPart(text: string): MessageV2.Part {
+  return {
+    id: PartID.ascending(),
+    sessionID: SessionID.make("s"),
+    messageID: MessageID.make("m"),
+    type: "text" as const,
+    text,
+  }
+}
+
+function createReasoningPart(text: string): MessageV2.Part {
+  return {
+    id: PartID.ascending(),
+    sessionID: SessionID.make("s"),
+    messageID: MessageID.make("m"),
+    type: "reasoning" as const,
+    text,
+    time: { start: 0 },
+  }
+}
+
+function createToolPart(tool: string, title: string, status: "completed" | "running" = "completed"): MessageV2.Part {
+  if (status === "completed") {
+    return {
+      id: PartID.ascending(),
+      sessionID: SessionID.make("s"),
+      messageID: MessageID.make("m"),
+      type: "tool" as const,
+      callID: "c1",
+      tool,
+      state: {
+        status: "completed",
+        input: {},
+        output: "",
+        title,
+        metadata: {},
+        time: { start: 0, end: 1 },
+      },
+    }
+  }
+  return {
+    id: PartID.ascending(),
+    sessionID: SessionID.make("s"),
+    messageID: MessageID.make("m"),
+    type: "tool" as const,
+    callID: "c1",
+    tool,
+    state: {
+      status: "running",
+      input: {},
+      time: { start: 0 },
+    },
+  }
+}
+
+function createStepStartPart(): MessageV2.Part {
+  return {
+    id: PartID.ascending(),
+    sessionID: SessionID.make("s"),
+    messageID: MessageID.make("m"),
+    type: "step-start" as const,
+  }
+}
+
+function createStepFinishPart(): MessageV2.Part {
+  return {
+    id: PartID.ascending(),
+    sessionID: SessionID.make("s"),
+    messageID: MessageID.make("m"),
+    type: "step-finish" as const,
+    reason: "done",
+    cost: 0,
+    tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
+  }
+}
+
+describe("extractResponseText", () => {
+  test("returns text from text part", () => {
+    const parts = [createTextPart("Hello world")]
+    expect(extractResponseText(parts)).toBe("Hello world")
+  })
+
+  test("returns last text part when multiple exist", () => {
+    const parts = [createTextPart("First"), createTextPart("Last")]
+    expect(extractResponseText(parts)).toBe("Last")
+  })
+
+  test("returns text even when tool parts follow", () => {
+    const parts = [createTextPart("I'll help with that."), createToolPart("todowrite", "3 todos")]
+    expect(extractResponseText(parts)).toBe("I'll help with that.")
+  })
+
+  test("returns null for reasoning-only response (signals summary needed)", () => {
+    const parts = [createReasoningPart("Let me think about this...")]
+    expect(extractResponseText(parts)).toBeNull()
+  })
+
+  test("returns null for tool-only response (signals summary needed)", () => {
+    // This is the exact scenario from the bug report - todowrite with no text
+    const parts = [createToolPart("todowrite", "8 todos")]
+    expect(extractResponseText(parts)).toBeNull()
+  })
+
+  test("returns null for multiple completed tools", () => {
+    const parts = [
+      createToolPart("read", "src/file.ts"),
+      createToolPart("edit", "src/file.ts"),
+      createToolPart("bash", "bun test"),
+    ]
+    expect(extractResponseText(parts)).toBeNull()
+  })
+
+  test("returns null for running tool parts (signals summary needed)", () => {
+    const parts = [createToolPart("bash", "", "running")]
+    expect(extractResponseText(parts)).toBeNull()
+  })
+
+  test("throws on empty array", () => {
+    expect(() => extractResponseText([])).toThrow("no parts returned")
+  })
+
+  test("returns null for step-start only", () => {
+    const parts = [createStepStartPart()]
+    expect(extractResponseText(parts)).toBeNull()
+  })
+
+  test("returns null for step-finish only", () => {
+    const parts = [createStepFinishPart()]
+    expect(extractResponseText(parts)).toBeNull()
+  })
+
+  test("returns null for step-start and step-finish", () => {
+    const parts = [createStepStartPart(), createStepFinishPart()]
+    expect(extractResponseText(parts)).toBeNull()
+  })
+
+  test("returns text from multi-step response", () => {
+    const parts = [
+      createStepStartPart(),
+      createToolPart("read", "src/file.ts"),
+      createTextPart("Done"),
+      createStepFinishPart(),
+    ]
+    expect(extractResponseText(parts)).toBe("Done")
+  })
+
+  test("prefers text over reasoning when both present", () => {
+    const parts = [createReasoningPart("Internal thinking..."), createTextPart("Final answer")]
+    expect(extractResponseText(parts)).toBe("Final answer")
+  })
+
+  test("prefers text over tools when both present", () => {
+    const parts = [createToolPart("read", "src/file.ts"), createTextPart("Here's what I found")]
+    expect(extractResponseText(parts)).toBe("Here's what I found")
+  })
+})
+
+describe("formatPromptTooLargeError", () => {
+  test("formats error without files", () => {
+    const result = formatPromptTooLargeError([])
+    expect(result).toBe("PROMPT_TOO_LARGE: The prompt exceeds the model's context limit.")
+  })
+
+  test("formats error with files (base64 content)", () => {
+    // Base64 is ~33% larger than original, so we multiply by 0.75 to get original size
+    // 400 KB base64 = 300 KB original, 200 KB base64 = 150 KB original
+    const files = [
+      { filename: "screenshot.png", content: "a".repeat(400 * 1024) },
+      { filename: "diagram.png", content: "b".repeat(200 * 1024) },
+    ]
+    const result = formatPromptTooLargeError(files)
+
+    expect(result).toStartWith("PROMPT_TOO_LARGE: The prompt exceeds the model's context limit.")
+    expect(result).toInclude("Files in prompt:")
+    expect(result).toInclude("screenshot.png (300 KB)")
+    expect(result).toInclude("diagram.png (150 KB)")
+  })
+
+  test("lists all files when multiple present", () => {
+    // Base64 sizes: 4KB -> 3KB, 8KB -> 6KB, 12KB -> 9KB
+    const files = [
+      { filename: "img1.png", content: "x".repeat(4 * 1024) },
+      { filename: "img2.jpg", content: "y".repeat(8 * 1024) },
+      { filename: "img3.gif", content: "z".repeat(12 * 1024) },
+    ]
+    const result = formatPromptTooLargeError(files)
+
+    expect(result).toInclude("img1.png (3 KB)")
+    expect(result).toInclude("img2.jpg (6 KB)")
+    expect(result).toInclude("img3.gif (9 KB)")
+  })
+})