docs: correct historical bundler command names

Use the dotted command names recorded in the bundler SDD snapshot.

Assisted-by: GitHub Copilot (model: GPT-6 Sol, autonomous)
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: mnriem

docs/guides/agentic-sdlc.md

@@ -111,8 +111,8 @@ design documents.
 
 ★ The [bundler SDD snapshot](https://github.com/github/spec-kit/commit/3fd1e54d4b237af6124bb967e2eae24c93685a89)
 illustrates the deeper path: its plan, research, data model, contracts, and
-tasks made the design actionable through `/speckit-plan` and
-`/speckit-tasks`. This shows where Spec Kit itself was used without
+tasks made the design actionable through `/speckit.plan` and
+`/speckit.tasks`. This shows where Spec Kit itself was used without
 presenting that level of detail as the default for every change.
 
 ### 4. Development: make reviewable changes