fix: add permissionMode: acceptEdits to worktree agents (#1334)

Worktree agents (gsd-executor, gsd-debugger) prompt for edit permissions
on every new directory they touch, even when the user has "accept edits"
enabled. This is caused by Claude Code's directory-scoped permission
model not propagating to worktree paths.

Setting permissionMode: acceptEdits in the agent frontmatter tells Claude
Code to auto-approve file edits for these agents, bypassing the per-
directory prompts. This is safe because these agents are already granted
Write/Edit in their tools list and are spawned in isolated worktrees.

- Add permissionMode: acceptEdits to gsd-executor.md frontmatter
- Add permissionMode: acceptEdits to gsd-debugger.md frontmatter
- Add regression tests verifying worktree agents have the field
- Add test ensuring all isolation="worktree" spawns are covered

Upstream: anthropics/claude-code#29110, anthropics/claude-code#28041

Fixes #1334

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

agents/gsd-debugger.md

@@ -2,6 +2,7 @@
 name: gsd-debugger
 description: Investigates bugs using scientific method, manages debug sessions, handles checkpoints. Spawned by /gsd:debug orchestrator.
 tools: Read, Write, Edit, Bash, Grep, Glob, WebSearch
+permissionMode: acceptEdits
 color: orange
 # hooks:
 #   PostToolUse:

agents/gsd-executor.md

@@ -2,6 +2,7 @@
 name: gsd-executor
 description: Executes GSD plans with atomic commits, deviation handling, checkpoint protocols, and state management. Spawned by execute-phase orchestrator or execute-plan command.
 tools: Read, Write, Edit, Bash, Grep, Glob
+permissionMode: acceptEdits
 color: yellow
 # hooks:
 #   PostToolUse: