docs(skill): document fn_workflow_list / fn_workflow_select engine tools

skill-sync.test.ts ("engine-tools.md documents all engine session-scoped
tools") scans the engine sources for `name: "fn_*"` and requires each to appear
in packages/cli/skill/fusion/references/engine-tools.md. The two new workflow
tools were added to agent-tools.ts/executor without a doc entry, so the sync
test failed (masked earlier by the dashboard build break). Add both to the
shared agent-tools table.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/cli/skill/fusion/references/engine-tools.md

@@ -15,6 +15,8 @@ These tools are **not** part of the user-invokable extension surface. They are i
 | `fn_task_log` | executor, heartbeat | Write significant task log entries | `message` (string), `outcome?` (string) |
 | `fn_task_document_write` | triage, executor, heartbeat | Save/update a named task document revision | `key` (string), `content` (string), `author?` (string) |
 | `fn_task_document_read` | triage, executor, heartbeat | Read one task document or list all | `key?` (string) |
+| `fn_workflow_list` | executor | List the project's custom workflows (read-only built-ins plus user definitions) | none |
+| `fn_workflow_select` | executor | Assign a custom workflow to a task (defaults to the current task) | `workflow_id` (string), `task_id?` (string) |
 | `fn_memory_search` | triage, executor, heartbeat | Search project memory plus per-agent layered memory snippets | `query` (string), `limit?` (number) |
 | `fn_memory_get` | triage, executor, heartbeat | Read a bounded memory file window (including bounded per-agent layered paths) | `path` (string), `startLine?` (number), `lineCount?` (number) |
 | `fn_memory_append` | executor, heartbeat (when writable backend enabled) | Append memory notes with explicit scope: `scope="agent"` for private operating context, `scope="project"` for workspace-wide durable knowledge | `scope?` (`project` \| `agent`), `layer` (`long-term` \| `daily`), `content` (string) |