Feature: Deferred skill discovery to reduce context window overhead

Problem

Every message in a Claude Code session includes the full skill catalog in <system-reminder> blocks. With plugins and custom commands, this can be 50-100+ skill entries injected into every single message — consuming ~4-5K tokens of context window per message that could be used for actual conversation.

This causes noticeably faster context compaction, especially in sessions with heavy tool use (where system-reminders are injected frequently). Users lose chat history much sooner than expected.

Current behavior

User message arrives
  → Platform injects ALL skill names + descriptions into system-reminder
  → Agent scans full list to find relevant skills
  → Agent invokes Skill tool for the 1-2 that match
  → 98% of the injected skill catalog was wasted context

Proposed behavior

Deferred skill loading, similar to how ToolSearch works for deferred tools:

1. Per-message injection: Only skill names (no descriptions) — or better, nothing at all
2. On-demand discovery: A SkillSearch mechanism (or extend ToolSearch) that takes a query and returns matching skill names + descriptions
3. Invocation: Skill tool works exactly as today — invoke by name, content loads on demand

User message arrives
  → Lightweight skill index (names only, ~500 bytes) or nothing
  → Agent uses SkillSearch("building UI components") → returns "frontend-design"
  → Agent invokes Skill tool as today
  → 95% context savings

Impact

• Context window: ~4-5K tokens saved per message (50-100 skills × ~50 tokens each)
• Session longevity: Significantly longer conversations before compaction
• Scalability: Plugin ecosystem can grow without degrading session quality
• No functionality loss: All skills remain available, just discovered on-demand

Environment

• Windows 11, Claude Code CLI + Desktop
• 7 plugins enabled (superpowers, frontend-design, code-simplifier, typescript-lsp, pyright-lsp, accesslint, accessibility-agents)
• 26 custom commands
• Total: ~70+ skills injected per message

Workaround

Currently none — disabling plugins removes both the catalog AND the ability to invoke those skills. They're coupled.