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/session/instruction.test.ts

@@ -0,0 +1,170 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test"
+import path from "path"
+import { InstructionPrompt } from "../../src/session/instruction"
+import { Instance } from "../../src/project/instance"
+import { Global } from "../../src/global"
+import { tmpdir } from "../fixture/fixture"
+
+describe("InstructionPrompt.resolve", () => {
+  test("returns empty when AGENTS.md is at project root (already in systemPaths)", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "AGENTS.md"), "# Root Instructions")
+        await Bun.write(path.join(dir, "src", "file.ts"), "const x = 1")
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const system = await InstructionPrompt.systemPaths()
+        expect(system.has(path.join(tmp.path, "AGENTS.md"))).toBe(true)
+
+        const results = await InstructionPrompt.resolve([], path.join(tmp.path, "src", "file.ts"), "test-message-1")
+        expect(results).toEqual([])
+      },
+    })
+  })
+
+  test("returns AGENTS.md from subdirectory (not in systemPaths)", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "subdir", "AGENTS.md"), "# Subdir Instructions")
+        await Bun.write(path.join(dir, "subdir", "nested", "file.ts"), "const x = 1")
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const system = await InstructionPrompt.systemPaths()
+        expect(system.has(path.join(tmp.path, "subdir", "AGENTS.md"))).toBe(false)
+
+        const results = await InstructionPrompt.resolve(
+          [],
+          path.join(tmp.path, "subdir", "nested", "file.ts"),
+          "test-message-2",
+        )
+        expect(results.length).toBe(1)
+        expect(results[0].filepath).toBe(path.join(tmp.path, "subdir", "AGENTS.md"))
+      },
+    })
+  })
+
+  test("doesn't reload AGENTS.md when reading it directly", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "subdir", "AGENTS.md"), "# Subdir Instructions")
+        await Bun.write(path.join(dir, "subdir", "nested", "file.ts"), "const x = 1")
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const filepath = path.join(tmp.path, "subdir", "AGENTS.md")
+        const system = await InstructionPrompt.systemPaths()
+        expect(system.has(filepath)).toBe(false)
+
+        const results = await InstructionPrompt.resolve([], filepath, "test-message-2")
+        expect(results).toEqual([])
+      },
+    })
+  })
+})
+
+describe("InstructionPrompt.systemPaths OPENCODE_CONFIG_DIR", () => {
+  let originalConfigDir: string | undefined
+
+  beforeEach(() => {
+    originalConfigDir = process.env["OPENCODE_CONFIG_DIR"]
+  })
+
+  afterEach(() => {
+    if (originalConfigDir === undefined) {
+      delete process.env["OPENCODE_CONFIG_DIR"]
+    } else {
+      process.env["OPENCODE_CONFIG_DIR"] = originalConfigDir
+    }
+  })
+
+  test("prefers OPENCODE_CONFIG_DIR AGENTS.md over global when both exist", async () => {
+    await using profileTmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "AGENTS.md"), "# Profile Instructions")
+      },
+    })
+    await using globalTmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "AGENTS.md"), "# Global Instructions")
+      },
+    })
+    await using projectTmp = await tmpdir()
+
+    process.env["OPENCODE_CONFIG_DIR"] = profileTmp.path
+    const originalGlobalConfig = Global.Path.config
+    ;(Global.Path as { config: string }).config = globalTmp.path
+
+    try {
+      await Instance.provide({
+        directory: projectTmp.path,
+        fn: async () => {
+          const paths = await InstructionPrompt.systemPaths()
+          expect(paths.has(path.join(profileTmp.path, "AGENTS.md"))).toBe(true)
+          expect(paths.has(path.join(globalTmp.path, "AGENTS.md"))).toBe(false)
+        },
+      })
+    } finally {
+      ;(Global.Path as { config: string }).config = originalGlobalConfig
+    }
+  })
+
+  test("falls back to global AGENTS.md when OPENCODE_CONFIG_DIR has no AGENTS.md", async () => {
+    await using profileTmp = await tmpdir()
+    await using globalTmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "AGENTS.md"), "# Global Instructions")
+      },
+    })
+    await using projectTmp = await tmpdir()
+
+    process.env["OPENCODE_CONFIG_DIR"] = profileTmp.path
+    const originalGlobalConfig = Global.Path.config
+    ;(Global.Path as { config: string }).config = globalTmp.path
+
+    try {
+      await Instance.provide({
+        directory: projectTmp.path,
+        fn: async () => {
+          const paths = await InstructionPrompt.systemPaths()
+          expect(paths.has(path.join(profileTmp.path, "AGENTS.md"))).toBe(false)
+          expect(paths.has(path.join(globalTmp.path, "AGENTS.md"))).toBe(true)
+        },
+      })
+    } finally {
+      ;(Global.Path as { config: string }).config = originalGlobalConfig
+    }
+  })
+
+  test("uses global AGENTS.md when OPENCODE_CONFIG_DIR is not set", async () => {
+    await using globalTmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "AGENTS.md"), "# Global Instructions")
+      },
+    })
+    await using projectTmp = await tmpdir()
+
+    delete process.env["OPENCODE_CONFIG_DIR"]
+    const originalGlobalConfig = Global.Path.config
+    ;(Global.Path as { config: string }).config = globalTmp.path
+
+    try {
+      await Instance.provide({
+        directory: projectTmp.path,
+        fn: async () => {
+          const paths = await InstructionPrompt.systemPaths()
+          expect(paths.has(path.join(globalTmp.path, "AGENTS.md"))).toBe(true)
+        },
+      })
+    } finally {
+      ;(Global.Path as { config: string }).config = originalGlobalConfig
+    }
+  })
+})