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/tool/skill.test.ts

@@ -0,0 +1,167 @@
+import { afterEach, describe, expect, test } from "bun:test"
+import path from "path"
+import { pathToFileURL } from "url"
+import type { Permission } from "../../src/permission"
+import type { Tool } from "../../src/tool/tool"
+import { Instance } from "../../src/project/instance"
+import { SkillTool } from "../../src/tool/skill"
+import { tmpdir } from "../fixture/fixture"
+import { SessionID, MessageID } from "../../src/session/schema"
+
+const baseCtx: Omit<Tool.Context, "ask"> = {
+  sessionID: SessionID.make("ses_test"),
+  messageID: MessageID.make(""),
+  callID: "",
+  agent: "build",
+  abort: AbortSignal.any([]),
+  messages: [],
+  metadata: () => {},
+}
+
+afterEach(async () => {
+  await Instance.disposeAll()
+})
+
+describe("tool.skill", () => {
+  test("description lists skill location URL", async () => {
+    await using tmp = await tmpdir({
+      git: true,
+      init: async (dir) => {
+        const skillDir = path.join(dir, ".opencode", "skill", "tool-skill")
+        await Bun.write(
+          path.join(skillDir, "SKILL.md"),
+          `---
+name: tool-skill
+description: Skill for tool tests.
+---
+
+# Tool Skill
+`,
+        )
+      },
+    })
+
+    const home = process.env.OPENCODE_TEST_HOME
+    process.env.OPENCODE_TEST_HOME = tmp.path
+
+    try {
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const tool = await SkillTool.init()
+          const skillPath = path.join(tmp.path, ".opencode", "skill", "tool-skill", "SKILL.md")
+          expect(tool.description).toContain(`**tool-skill**: Skill for tool tests.`)
+        },
+      })
+    } finally {
+      process.env.OPENCODE_TEST_HOME = home
+    }
+  })
+
+  test("description sorts skills by name and is stable across calls", async () => {
+    await using tmp = await tmpdir({
+      git: true,
+      init: async (dir) => {
+        for (const [name, description] of [
+          ["zeta-skill", "Zeta skill."],
+          ["alpha-skill", "Alpha skill."],
+          ["middle-skill", "Middle skill."],
+        ]) {
+          const skillDir = path.join(dir, ".opencode", "skill", name)
+          await Bun.write(
+            path.join(skillDir, "SKILL.md"),
+            `---
+name: ${name}
+description: ${description}
+---
+
+# ${name}
+`,
+          )
+        }
+      },
+    })
+
+    const home = process.env.OPENCODE_TEST_HOME
+    process.env.OPENCODE_TEST_HOME = tmp.path
+
+    try {
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const first = await SkillTool.init()
+          const second = await SkillTool.init()
+
+          expect(first.description).toBe(second.description)
+
+          const alpha = first.description.indexOf("**alpha-skill**: Alpha skill.")
+          const middle = first.description.indexOf("**middle-skill**: Middle skill.")
+          const zeta = first.description.indexOf("**zeta-skill**: Zeta skill.")
+
+          expect(alpha).toBeGreaterThan(-1)
+          expect(middle).toBeGreaterThan(alpha)
+          expect(zeta).toBeGreaterThan(middle)
+        },
+      })
+    } finally {
+      process.env.OPENCODE_TEST_HOME = home
+    }
+  })
+
+  test("execute returns skill content block with files", async () => {
+    await using tmp = await tmpdir({
+      git: true,
+      init: async (dir) => {
+        const skillDir = path.join(dir, ".opencode", "skill", "tool-skill")
+        await Bun.write(
+          path.join(skillDir, "SKILL.md"),
+          `---
+name: tool-skill
+description: Skill for tool tests.
+---
+
+# Tool Skill
+
+Use this skill.
+`,
+        )
+        await Bun.write(path.join(skillDir, "scripts", "demo.txt"), "demo")
+      },
+    })
+
+    const home = process.env.OPENCODE_TEST_HOME
+    process.env.OPENCODE_TEST_HOME = tmp.path
+
+    try {
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const tool = await SkillTool.init()
+          const requests: Array<Omit<Permission.Request, "id" | "sessionID" | "tool">> = []
+          const ctx: Tool.Context = {
+            ...baseCtx,
+            ask: async (req) => {
+              requests.push(req)
+            },
+          }
+
+          const result = await tool.execute({ name: "tool-skill" }, ctx)
+          const dir = path.join(tmp.path, ".opencode", "skill", "tool-skill")
+          const file = path.resolve(dir, "scripts", "demo.txt")
+
+          expect(requests.length).toBe(1)
+          expect(requests[0].permission).toBe("skill")
+          expect(requests[0].patterns).toContain("tool-skill")
+          expect(requests[0].always).toContain("tool-skill")
+
+          expect(result.metadata.dir).toBe(dir)
+          expect(result.output).toContain(`<skill_content name="tool-skill">`)
+          expect(result.output).toContain(`Base directory for this skill: ${pathToFileURL(dir).href}`)
+          expect(result.output).toContain(`<file>${file}</file>`)
+        },
+      })
+    } finally {
+      process.env.OPENCODE_TEST_HOME = home
+    }
+  })
+})