fix(dispatcher): rename Task→Agent in allowed-tools, workflow prose, and agent tools frontmatter

Fixes #3168

The Claude Code subagent dispatcher tool is named `Agent` (with `subagent_type`
parameter). The `Task*` namespace (TaskCreate, TaskList, TaskGet, TaskUpdate,
TaskOutput, TaskStop) is the separate task-tracker. GSD's commands, workflows,
and agents were partially migrated and still referenced `- Task` / `Task(` in
55 files, causing orchestrators to silently fall back to inline execution when
no `Task` tool appeared on their tool surface.

Changes:
- `commands/gsd/*.md` allowed-tools: replaced `- Task` with `- Agent` in 24
  files; removed duplicate `- Task` from autonomous.md (already had `- Agent`)
- `get-shit-done/workflows/*.md`: replaced dispatcher `Task(` → `Agent(` in
  29 workflow files (~133 call sites); TaskCreate/List/Get/Update/Output/Stop
  left untouched
- `agents/gsd-debug-session-manager.md`: replaced `Task` → `Agent` in tools
  frontmatter (the only remaining agent with the wrong name)

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

get-shit-done/workflows/execute-phase/steps/codebase-drift-gate.md

@@ -51,7 +51,7 @@ AGENT_SKILLS_MAPPER=$(gsd-sdk query agent-skills gsd-codebase-mapper)
 Then spawn `gsd-codebase-mapper` agents with the `--paths` hint:
 
 ```text
-Task(
+Agent(
   subagent_type="gsd-codebase-mapper",
   description="Incremental codebase remap (drift)",
   prompt="Focus: arch
@@ -64,7 +64,7 @@ ${AGENT_SKILLS_MAPPER}"
 )
 ```
 
-> **ORCHESTRATOR RULE — CODEX RUNTIME**: After calling Task() above, stop working on this task immediately. Do not read more files, edit code, or run tests related to this task while the subagent is active. Wait for the subagent to return its result. This prevents duplicate work, conflicting edits, and wasted context. Only resume when the subagent result is available.
+> **ORCHESTRATOR RULE — CODEX RUNTIME**: After calling Agent() above, stop working on this task immediately. Do not read more files, edit code, or run tests related to this task while the subagent is active. Wait for the subagent to return its result. This prevents duplicate work, conflicting edits, and wasted context. Only resume when the subagent result is available.
 
 If the spawn fails or the agent reports an error: log `Codebase drift
 auto-remap failed: {reason}` and continue to `verify_phase_goal`. The phase