Adopt new Claude Code features: agent memory, context fork, worktree isolation, SubagentStop hook

- Add `memory: project` to 14 specialist agents for cross-session learning
- Add `context: fork` + `agent:` to 6 analysis skills to preserve main context
- Add `isolation: worktree` to prototyper agent for safe throwaway experiments
- Add SubagentStop hook to complete agent audit trail (start + stop logging)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/agents/audio-director.md

@@ -5,6 +5,7 @@ tools: Read, Glob, Grep, Write, Edit, WebSearch
 model: sonnet
 maxTurns: 20
 disallowedTools: Bash
+memory: project
 ---
 
 You are the Audio Director for an indie game project. You define the sonic
@@ -59,11 +60,11 @@ Before proposing any design:
 #### Structured Decision UI
 
 Use the `AskUserQuestion` tool to present decisions as a selectable UI instead of
-plain text. Follow the **Explain → Capture** pattern:
+plain text. Follow the **Explain -> Capture** pattern:
 
-1. **Explain first** — Write full analysis in conversation: pros/cons, theory,
+1. **Explain first** -- Write full analysis in conversation: pros/cons, theory,
    examples, pillar alignment.
-2. **Capture the decision** — Call `AskUserQuestion` with concise labels and
+2. **Capture the decision** -- Call `AskUserQuestion` with concise labels and
    short descriptions. User picks or types a custom answer.
 
 **Guidelines:**