chore(void): remove dead linkSkillsForAgents (#241)

## What

This removes the exported linkSkillsForAgents function from
packages/void/src/cli/skills.ts and drops the detectAgents import that
only that function used.

## Why

The function is dead code. linkSkillsForAgents is never called anywhere
in the monorepo. It was superseded by linkSkillsForSpecificAgents, which
is what void init actually calls, and its own doc comment falsely
claimed it was used by void init. With the function gone, the
detectAgents import became unused, so it is removed as well.

## Safety

There is no behavior change. The function had no callers. The shared
helpers parseSkills and linkSkills, the sibling
linkSkillsForSpecificAgents, and the getPackageDir, AgentConfig, and log
imports are all untouched because they are still used.

## Verification

There are zero references to linkSkillsForAgents across packages
including tests. The void package typechecks cleanly with tsgo and
passes oxlint. The change is one insertion and 26 deletions.

Author: shulaoda

packages/void/src/cli/skills.ts

@@ -8,7 +8,7 @@ import {
 } from 'node:fs';
 import { log } from '@clack/prompts';
 import { join, relative } from 'pathe';
-import { detectAgents, getPackageDir, type AgentConfig } from './agents.ts';
+import { getPackageDir, type AgentConfig } from './agents.ts';
 
 type SkillInfo = {
   dirName: string;
@@ -82,31 +82,6 @@ function linkSkills(
   return linked;
 }
 
-/**
- * Link skills for all detected agents. Returns total number of newly linked skills.
- * Used by `void init` (interactive flow and `--agents` flag).
- */
-export function linkSkillsForAgents(root: string): number {
-  const packageDir = getPackageDir();
-  const skillsDir = join(packageDir, 'skills');
-  const skills = parseSkills(skillsDir);
-  if (skills.length === 0) {
-    return 0;
-  }
-
-  const detected = detectAgents(root);
-  if (detected.length === 0) {
-    return 0;
-  }
-
-  let totalLinked = 0;
-  for (const agent of detected) {
-    log.info(`${agent.displayName} → ${agent.skillsDir}`);
-    totalLinked += linkSkills(root, skillsDir, skills, agent.skillsDir);
-  }
-  return totalLinked;
-}
-
 export function linkSkillsForSpecificAgents(root: string, agents: Array<AgentConfig>): number {
   const packageDir = getPackageDir();
   const skillsDir = join(packageDir, 'skills');