docs: add workflows reference, reorganize into docs/reference/, and add --version flag (#2244)

* docs: add workflows reference, reorganize into docs/reference/, and add --version flag

- Move integrations.md, extensions.md, presets.md into docs/reference/
- New docs/reference/workflows.md: command reference for all workflow
  commands, built-in SDD Cycle workflow with Mermaid diagram, step types,
  expressions, input types, state/resume, and FAQ
- Rename workflow input feature_name to spec with prompt 'Describe what
  you want to build' to match speckit.specify command terminology
- Add --version / -V flag to root specify command with tests
- Update docs/toc.yml, README.md links, and docs/upgrade.md cross-reference
  to use reference/ paths
- Add workflow command to README CLI reference table

* docs: update speckit_version requirement to >=0.7.2 in workflow example

src/specify_cli/__init__.py

@@ -351,8 +351,16 @@ def show_banner():
     console.print(Align.center(Text(TAGLINE, style="italic bright_yellow")))
     console.print()
 
+def _version_callback(value: bool):
+    if value:
+        console.print(f"specify {get_speckit_version()}")
+        raise typer.Exit()
+
 @app.callback()
-def callback(ctx: typer.Context):
+def callback(
+    ctx: typer.Context,
+    version: bool = typer.Option(False, "--version", "-V", callback=_version_callback, is_eager=True, help="Show version and exit."),
+):
     """Show banner when no subcommand is provided."""
     if ctx.invoked_subcommand is None and "--help" not in sys.argv and "-h" not in sys.argv:
         show_banner()

src/specify_cli/workflows/expressions.py

@@ -255,7 +255,7 @@ def evaluate_expression(template: str, context: Any) -> Any:
     ----------
     template:
         The template string (e.g., ``"{{ steps.plan.output.task_count }}"``
-        or ``"Processed {{ inputs.feature_name }}"``.
+        or ``"Processed {{ inputs.spec }}"``.
     context:
         A ``StepContext`` or compatible object.