Fix review comments: update agent file extension reference and line lengths

- Update .agent.md extension references in AGENTS.md and technical-writer.agent.md
- Remove 'Propagatable' from .cspell.yaml (not used in ReqStream)
- Fix MD013 line length violations in AGENTS.md and technical-writer.agent.md

Author: Copilot

.cspell.yaml

@@ -33,7 +33,6 @@ words:
   - NuGet
   - Pandoc
   - pagetitle
-  - Propagatable
   - reqstream
   - ReqStream
   - SARIF

.github/agents/technical-writer.agent.md

@@ -36,7 +36,8 @@ Invoke the technical-writer for:
 - **All markdown files**: Use reference-style links `[text][ref]` with `[ref]: url` at document end
 - **Exceptions**:
   - **README.md**: Use absolute URLs in the links (shipped in NuGet package)
-  - **AI agent markdown files** (`.github/agents/*.md`): Use inline links `[text](url)` so URLs are visible in agent context
+  - **AI agent markdown files** (`.github/agents/*.agent.md`): Use inline links `[text](url)` so
+    URLs are visible in agent context
 - Max 120 characters per line
 - Lists require blank lines (MD032)
 

AGENTS.md

@@ -118,7 +118,8 @@ build.bat     # Windows
 
 ## Markdown Link Style
 
-- **AI agent markdown files** (`.github/agents/*.md`): Use inline links `[text](url)` so URLs are visible in agent context
+- **AI agent markdown files** (`.github/agents/*.agent.md`): Use inline links `[text](url)` so
+  URLs are visible in agent context
 - **README.md**: Use absolute URLs (shipped in NuGet package)
 - **All other markdown files**: Use reference-style links `[text][ref]` with `[ref]: url` at document end