fix: add explicit agent type listings to prevent fallback after /clear (#949) (#1139)

After /clear, Claude Code sometimes loses awareness of custom agent types
and falls back to 'general-purpose'. This happens because the model doesn't
re-read .claude/agents/ after context reset.

Added <available_agent_types> sections to:
- execute-phase.md: lists all 12 valid GSD agent types with descriptions
- plan-phase.md: lists the 3 agent types used during planning

The explicit listing in workflow instructions ensures the model always has
an unambiguous reference to valid agent types, regardless of whether
.claude/agents/ was re-read after /clear.

Fixes #949

get-shit-done/workflows/execute-phase.md

@@ -10,6 +10,24 @@ Orchestrator coordinates, not executes. Each subagent loads the full execute-pla
 Read STATE.md before any operation to load project context.
 </required_reading>
 
+<available_agent_types>
+These are the valid GSD subagent types registered in .claude/agents/ (or equivalent for your runtime).
+Always use the exact name from this list — do not fall back to 'general-purpose' or other built-in types:
+
+- gsd-executor — Executes plan tasks, commits, creates SUMMARY.md
+- gsd-verifier — Verifies phase completion, checks quality gates
+- gsd-planner — Creates detailed plans from phase scope
+- gsd-phase-researcher — Researches technical approaches for a phase
+- gsd-plan-checker — Reviews plan quality before execution
+- gsd-debugger — Diagnoses and fixes issues
+- gsd-codebase-mapper — Maps project structure and dependencies
+- gsd-integration-checker — Checks cross-phase integration
+- gsd-nyquist-auditor — Validates verification coverage
+- gsd-ui-researcher — Researches UI/UX approaches
+- gsd-ui-checker — Reviews UI implementation quality
+- gsd-ui-auditor — Audits UI against design requirements
+</available_agent_types>
+
 <process>
 
 <step name="initialize" priority="first">

get-shit-done/workflows/plan-phase.md

@@ -8,6 +8,13 @@ Read all files referenced by the invoking prompt's execution_context before star
 @~/.claude/get-shit-done/references/ui-brand.md
 </required_reading>
 
+<available_agent_types>
+Valid GSD subagent types (use exact names — do not fall back to 'general-purpose'):
+- gsd-phase-researcher — Researches technical approaches for a phase
+- gsd-planner — Creates detailed plans from phase scope
+- gsd-plan-checker — Reviews plan quality before execution
+</available_agent_types>
+
 <process>
 
 ## 1. Initialize