fix(slashcommand): deduplicate opencode command aliases

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

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

src/tools/slashcommand/command-discovery.test.ts

@@ -204,4 +204,35 @@ Use ancestor command.
     expect(ancestorCommand?.scope).toBe("opencode-project")
     expect(ancestorCommand?.content).toContain("Use ancestor command.")
   })
+
+  it("deduplicates same-named opencode commands while keeping the higher-priority alias", () => {
+    const commandsRoot = join(projectDir, ".opencode")
+    const singularDir = join(commandsRoot, "command")
+    const pluralDir = join(commandsRoot, "commands")
+
+    mkdirSync(singularDir, { recursive: true })
+    mkdirSync(pluralDir, { recursive: true })
+    writeFileSync(
+      join(singularDir, "duplicate.md"),
+      `---
+description: Singular duplicate command
+---
+Use singular command.
+`,
+    )
+    writeFileSync(
+      join(pluralDir, "duplicate.md"),
+      `---
+description: Plural duplicate command
+---
+Use plural command.
+`,
+    )
+
+    const commands = discoverCommandsSync(projectDir)
+    const duplicates = commands.filter((command) => command.name === "duplicate")
+
+    expect(duplicates).toHaveLength(1)
+    expect(duplicates[0]?.content).toContain("Use plural command.")
+  })
 })

src/tools/slashcommand/command-discovery.ts

@@ -76,6 +76,22 @@ function discoverPluginCommands(options?: CommandDiscoveryOptions): CommandInfo[
   }))
 }
 
+function deduplicateCommandInfosByName(commands: CommandInfo[]): CommandInfo[] {
+  const seen = new Set<string>()
+  const deduplicatedCommands: CommandInfo[] = []
+
+  for (const command of commands) {
+    if (seen.has(command.name)) {
+      continue
+    }
+
+    seen.add(command.name)
+    deduplicatedCommands.push(command)
+  }
+
+  return deduplicatedCommands
+}
+
 export function discoverCommandsSync(
   directory?: string,
   options?: CommandDiscoveryOptions,
@@ -110,12 +126,12 @@ export function discoverCommandsSync(
     scope: "builtin",
   }))
 
-  return [
+  return deduplicateCommandInfosByName([
     ...projectCommands,
     ...userCommands,
     ...opencodeProjectCommands,
     ...opencodeGlobalCommands,
     ...builtinCommands,
     ...pluginCommands,
-  ]
+  ])
 }