Implement Collections feature for grouping related prompts, instructions, and chat modes (#232)

* Initial plan

* Implement core Collections feature with YAML parsing and README generation

Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>

* Complete Collections feature implementation with validation, tooling, and documentation

Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>

* Update generated README files to include collections instructions

* Fix YAML parsing logic bug: replace impossible condition with proper indentation check

Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>

* Refactor: Extract YAML parser to shared module and improve user experience

Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>

* fixing task and file permissions

* Better args handling

* Adding some more collections

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>
Co-authored-by: Aaron Powell <me@aaron-powell.com>

collections/devops-oncall.collection.yml

@@ -0,0 +1,18 @@
+id: devops-oncall
+name: DevOps On-Call
+description: A focused set of prompts, instructions, and a chat mode to help triage incidents and respond quickly with DevOps tools and Azure resources.
+tags: [devops, incident-response, oncall, azure]
+items:
+  - path: prompts/azure-resource-health-diagnose.prompt.md
+    kind: prompt
+  - path: instructions/devops-core-principles.instructions.md
+    kind: instruction
+  - path: instructions/containerization-docker-best-practices.instructions.md
+    kind: instruction
+  - path: chatmodes/azure-principal-architect.chatmode.md
+    kind: chat-mode
+  - path: prompts/multi-stage-dockerfile.prompt.md
+    kind: prompt
+display:
+  ordering: manual
+  show_badge: true