Fix markdown lint: fenced block languages, TOC entry, setext heading

Author: max-svistunov

docs/contributing/howto-organize-poc-output.md

@@ -11,7 +11,7 @@ Place results in `docs/design/<feature>/poc-results/`.
 Name files with a numeric prefix that reflects reading order.  Order them by
 usefulness for the human reviewer:
 
-```
+```text
 poc-results/
 ├── 01-poc-report.txt       — findings, methodology, implications
 ├── 02-conversation-log.txt  — human-readable record of the PoC

docs/contributing/templates/jira-ticket-template.md

@@ -12,7 +12,7 @@
 
 **Agentic tool instruction**: TODO
 
-```
+```text
 Read the "[section]" section in docs/design/<feature>/<feature>.md.
 Key files: [files].
 ```

docs/contributing/templates/spec-doc-template.md

@@ -37,7 +37,7 @@ TODO: User stories in "As a [role], I want [X], so that [Y]" format.
 
 TODO: Flow diagram showing the request/response path with the new feature.
 
-```
+```text
 TODO: flow diagram
 ```
 

docs/contributing/templates/spike-template.md

@@ -46,15 +46,15 @@ TODO: Use the format from `docs/contributing/templates/jira-ticket-template.md`.
 
 **Scope**: TODO
 
--
+- TODO
 
 **Acceptance criteria**: TODO
 
--
+- TODO
 
 **Agentic tool instruction**: TODO
 
-```
+```text
 Read the "[section]" section in docs/design/<feature>/<feature>.md.
 Key files: [files].
 ```
@@ -66,7 +66,7 @@ TODO: If a PoC was built, document what it does, what it proved, and how it dive
 ## What the PoC does
 
 **Important**: The PoC diverges from the production design in these ways:
--
+- TODO
 
 ## Results
 

docs/contributing_guide.md

@@ -10,6 +10,7 @@
 * [PR description](#pr-description)
 * [Definition of Done](#definition-of-done)
     * [A deliverable is to be considered “done” when](#a-deliverable-is-to-be-considered-done-when)
+* [Feature design process](#feature-design-process)
 * [AI assistants](#ai-assistants)
     * [“Mark” code with substantial AI-generated portions.](#mark-code-with-substantial-ai-generated-portions)
     * [Copyright and licence notices](#copyright-and-licence-notices)