fix: clarify numeric issue URL formatting in dispatcher workflow source

Agent-Logs-Url: https://github.com/github/gh-aw-firewall/sessions/9718b392-06e4-4d03-a68e-3bd948d876c2

Author: Copilot

.github/workflows/firewall-issue-dispatcher.md

@@ -82,9 +82,12 @@ For each **unprocessed** issue:
 2. **Comment on the original `github/gh-aw` issue** linking to the newly created tracking issue. Use this exact format:
    > 🔗 AWF tracking issue: https://github.com/github/gh-aw-firewall/issues/{NUMBER}
 
-   where `{NUMBER}` is replaced with **only the numeric issue number** (e.g., `1896`). Do NOT include the repository name, hash symbols, or any other text — just the number in the URL path. Use the `add_comment` safe output tool with `repo: "github/gh-aw"` and the original issue number.
+   `create_issue` may return a reference like `github/gh-aw-firewall#2159`. Extract only the trailing digits before composing the URL.
+   - Valid: `https://github.com/github/gh-aw-firewall/issues/2159`
+   - Invalid: `https://github.com/github/gh-aw-firewall/issues/github/gh-aw-firewall#2159`
+   - Invalid: `https://github.com/github/gh-aw-firewall/issues/#2159`
 
-   where `{NUMBER}` is replaced with **only the numeric issue number** (e.g., `1896`). Do NOT include the repository name, hash symbols, or any other text — just the number in the URL path. Use the `add_comment` safe output tool with `repo: "github/gh-aw"` and the original issue number.
+   Use the `add_comment` safe output tool with `repo: "github/gh-aw"` and the original issue number.
 
 ### 4. Report Results