fix(orchestrators): inline file contents in Task prompts
The @ file reference syntax does not expand across Task() boundaries.
Subagents receive literal @path strings instead of file contents.
Changed orchestrator→subagent handoffs to explicitly read files and
inline content before spawning:
- plan-phase → gsd-planner: STATE, ROADMAP, REQUIREMENTS, CONTEXT, RESEARCH
- plan-phase → gsd-plan-checker: PLAN files, REQUIREMENTS
- plan-phase → gsd-planner (revision): PLAN files
- execute-phase → gsd-executor: PLAN, STATE, config
Fixes #182
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
ce4fc96ff7