fix(agents): remove permissionMode that breaks Gemini CLI agent loading (#1522)

permissionMode: acceptEdits in gsd-executor and gsd-debugger frontmatter
is Claude Code-specific and causes Gemini CLI to hard-fail on agent load
with "Unrecognized key(s) in object: 'permissionMode'". The field also
has no effect in Claude Code (subagent Write permissions are controlled
at runtime level regardless). Remove it from both agents and update
tests to enforce cross-runtime compatibility.

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

agents/gsd-debugger.md

@@ -2,7 +2,6 @@
 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

@@ -2,7 +2,6 @@
 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: